(1) alcohols can be oxidised by an acidified solution of potassium dichromate(Vl). Aldehydes can be...

The following instructions are from an experimental procedure for the preparation of cyclohexenefrom cyclohexanol and concentrated phosphoric acid.Read these instructions and answer the questions that follow.

1 Place 25 cm3 of cyclohexanol into a round-bottomed flask with some porous pot to act as

anti-bumping granules. Add 10 cm3 of concentrated phosphoric acid carefully while shakingthe flask. Cool the flask under the tap if it gets too hot.Make sure the reagents are thoroughly mixed.

2 Set up an apparatus for simple distillation using this flask.

3 Warm the flask, gently at first, for about 15 minutes. Then increase the heating so thatcyclohexene begins to distil over. Collect the fraction that distils below 95 °C.

(a) State the purpose of the anti-bumping granules.

........................................................................................................................

........................................................................................................................(1)

1

(b) Name the part of the distillation apparatus where cyclohexene vapour is changed back intoa liquid.Draw a simple diagram of this part of the apparatus.

Name .............................................................................................................

Diagram

(2)

(Total 3 marks)

of 80

Some alcohols can be oxidised by an acidified solution of potassium dichromate(Vl).Aldehydes can be oxidised by Tollens’ reagent or by Fehling’s solution.

An unknown pure liquid A contains only a single alcohol.Outline a simple procedure to allow you to determine whether A is a primary, a secondary or atertiary alcohol.

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................(Total 3 marks)

2

This question is about cobalt chemistry.

(a) Consider the following reaction scheme that starts from [Co(H2O)6]2+ ions.W, X and Y are ions and Z is a compound.

For each of the reactions 1 to 4, identify a suitable reagent.

3

of 80

Identify W, X, Y and Z and write an equation for each of reactions 1 to 4.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

(Extra space) .................................................................................................

........................................................................................................................

........................................................................................................................(12)

(b) A flue-gas desulfurisation process involves the oxidation, by oxygen, of aqueous sulfate(IV)

ions (SO3 2–) into aqueous sulfate(VI) ions (SO4

2–). This reaction is catalysed by Co2+ ionsin an acidic aqueous solution.

Write an equation for the overall reaction of sulfate(IV) ions with oxygen to form sulfate(VI)ions.

Suggest why this overall reaction is faster in the presence of Co2+ ions.

of 80

Suggest a mechanism for the catalysed reaction by writing two equations involving Co2+

and Co3+ ions. You will need to use H+ ions and H2O to balance these two equations.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(4)

(Total 16 marks)

of 80

Salicylic acid can be used to make aspirin. Before using a sample of salicylic acid to makeaspirin, a student purified the acid by recrystallisation. The method for recrystallisation is outlinedbelow.

Step 1: The sample is dissolved in a minimum volume of hot water.Step 2: The solution is filtered hot.Step 3: The filtrate is cooled in ice to form crystals.Step 4: The crystals are collected by filtration, washed with cold water and left to dry.

Explain the purpose of each underlined point.

Minimum volume .....................................................................................................

.................................................................................................................................

Hot water ................................................................................................................

.................................................................................................................................

Filtered hot ..............................................................................................................

.................................................................................................................................

Cooled in ice ...........................................................................................................

.................................................................................................................................

Washed with cold water ..........................................................................................

.................................................................................................................................(Total 5 marks)

4

Salicylic acid, C6H4(OH)COOH, reacts with magnesium to produce magnesium salicylate andhydrogen.

(a) Complete the equation for this reaction.

C6H4(OH)COOH(1)

5

of 80

(b) In an alternative method for determining percentage purity, a student reacted a solution ofsalicylic acid with an excess of magnesium and collected the hydrogen gas that wasreleased.

Complete the diagram below to show an apparatus that could be used to collect andmeasure the volume of hydrogen gas produced.

(1)(Total 2 marks)

An experiment was carried out to determine the original concentration of iron(II) ions in a solutionthat had been stored in air. An excess of zinc and acid was added to this solution. The mixturewas then filtered to remove the excess zinc before titration.

(a) Suggest why the zinc and acid were added.

........................................................................................................................

........................................................................................................................(1)

6

(b) Explain why it was necessary to remove the excess zinc.

........................................................................................................................

........................................................................................................................(1)

(Total 2 marks)

of 80

(a) The iron(II) ions in well-water can be removed by oxidation using potassiummanganate(VII) in alkaline solution. A mixture containing solid iron(III) hydroxide and solidmanganese(IV) oxide is formed. These solid products can be removed by filtration underreduced pressure.

(i) Draw a diagram of the apparatus used for this filtration. Do not include the apparatusused to reduce the pressure.

(2)

7

(ii) An equation representing the oxidation reaction is given below.

3Fe2+(aq) + KMnO4(aq) + 5OH–(aq) + 2H2O(I) 3Fe(OH)3(s) + MnO2(s) + K+(aq)

Calculate the mass, in grams, of KMnO4 required to react with the iron(II) ions in 1.00

dm3 of well-water that has an iron(II) concentration of 0.225 mol dm–3.Give your answer to the appropriate precision.Show your working.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................(3)

(iii) In practice, a slight excess of potassium manganate(VII) is used to treat thewell-water.Although this treated water is safe to drink, this excess of potassium manganate(VII)is undesirable. Suggest one reason, other than colour, why the excess isundesirable.

...............................................................................................................

...............................................................................................................(1)

of 80

(b) Suggest one reason why the colour of potassium manganate(VII) solution can be a sourceof error when using a volumetric (graduated) flask to prepare a standard solution.

........................................................................................................................

........................................................................................................................(1)

(Total 7 marks)

When using potassium manganate(VII) in redox titrations with iron(II) ions it is essential that thereaction mixture is acidified. Normally, dilute sulfuric acid is used.

(a) State why an excess of hydrogen ions is added to the reaction mixture.

........................................................................................................................

........................................................................................................................(1)

8

(b) State why the acid used must not be ethanoic acid.

........................................................................................................................

........................................................................................................................(1)

(c) Explain why an indicator is not needed in this redox titration.

........................................................................................................................

........................................................................................................................(1)

(Total 3 marks)

A student prepared a sample of aspirin (melting point 135 °C) in the laboratory and attempted topurify it by recrystallisation. To check the purity of the aspirin the student determined its meltingpoint.

(a) State two observations, during this melting point determination, that would indicate that thesample is not pure.

Observation 1 .................................................................................................

........................................................................................................................

Observation 2 .................................................................................................

........................................................................................................................(2)

9

of 80

(b) Suggest why a pure sample of aspirin may sometimes appear to melt at a temperaturedifferent from 135 °C.

........................................................................................................................

........................................................................................................................(1)

(Total 3 marks)

(a) Some scientists thought that the waste water from a waste disposal factory contained twosodium halides.

They tested a sample of the waste water.

They added three reagents, one after the other, to the same test tube containing the wastewater.

The table below shows their results.

Reagent added Observations

1. Silver nitrate solution (acidifiedwith dilute nitric acid)

A cream precipitate formed

2. Dilute ammonia solution A yellow precipitate remained

3. Concentrated ammonia solution The yellow precipitate did notdissolve

10

(i) Identify the yellow precipitate that did not dissolve in concentrated ammonia solution.Write the simplest ionic equation for the formation of this precipitate from silver ionsand the correct halide ion.Identify the other sodium halide that must be present in this mixture of two sodiumhalides.

.............................................................................................................

.............................................................................................................

.............................................................................................................

.............................................................................................................(3)

(ii) Give one reason why the silver nitrate solution was acidified before it was used in thistest.

.............................................................................................................

.............................................................................................................

.............................................................................................................(1)

of 80

(iii) The method that the scientists used could not detect one type of halide ion. Identifythis halide ion.Give one reason for your answer.

.............................................................................................................

.............................................................................................................

.............................................................................................................

.............................................................................................................(2)

(b) The scientists thought that the waste water also contained dissolved barium ions. Anaqueous solution of sodium sulfate can be used to test for the presence of dissolvedbarium ions.

Write the simplest ionic equation for the reaction between barium ions and sulfate ions toform barium sulfate.

State what is observed in this reaction.

Give a use for barium sulfate in medicine and explain why this use is possible, given thatsolutions containing barium ions are poisonous.

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................(4)

of 80

(c) The scientists also analysed the exhaust gases from an incinerator used to destroy wastepoly(ethene).Mass spectrometry showed that there was a trace gas with a precise Mr = 28.03176 in theexhaust gases from the incinerator.

The table below contains some precise relative atomic mass data.

Atom Precise relative atomic mass

12C 12.00000

1H 1.00794

16O 15.99491

Use the data to show that the trace gas is ethene. Show your working.

Suggest why both ethene and carbon monoxide might have been identified as the tracegas if the scientists had used relative atomic masses to a precision of only one decimalplace.

Write an equation for the incomplete combustion of ethene to form carbon monoxide andwater only.

Ethene is used to make poly(ethene).Draw the displayed formula for the repeating unit of poly(ethene).Name this type of polymer.

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................(5)

(Total 15 marks)

of 80

Copper(II) sulfate solution, together with copper(II) carbonate (CuCO3) powder, can be used todetermine the identity of three solutions A, B and C. The three solutions are known to behydrochloric acid, barium chloride, and sodium chloride.

In Experiment 1 a small amount of copper(II) carbonate powder was added to each of the threesolutions.

In Experiment 2 a dropping pipette was used to add 2 cm3 of copper(II) sulfate solution to eachof the three solutions.

The results of these experiments are shown in the table below.

Experiment 1

Addition of copper(II)carbonate powder

Experiment 2Addition of copper(II)

sulfate solution

Solution A no visible change white precipitate

Solution B no visible change no visible change

Solution Ceffervescence

(bubbles of gas)no visible change

11

(a) Use the observations in the table to deduce which of the solutions, A, B or C is

hydrochloric acid ............................................................................................

barium chloride ..............................................................................................(2)

(b) Explain why a precipitate was formed when copper(II) sulfate solution was added tosolution A.Write an equation for the reaction that occurred.

Explanation ....................................................................................................

........................................................................................................................

Equation .........................................................................................................(2)

(c) Suggest the identity for the colourless gas produced when copper(II) carbonate powderwas added to solution C.

........................................................................................................................(1)

of 80

(d) Identify the two reagents that could be used in a test to confirm that the solutions containedchloride ions, not bromide ions. State what would be observed on addition of each reagent.

Reagent 1 ......................................................................................................

Observation 1 .................................................................................................

........................................................................................................................

Reagent 2 ......................................................................................................

Observation 2 .................................................................................................

........................................................................................................................(4)

(e) Copper(II) sulfate is toxic. Suggest one safety precaution you would take to minimise thishazard when wiping up a spillage of copper(II) sulfate solution.

........................................................................................................................(1)

(Total 10 marks)

(a) A solution of barium hydroxide is often used for the titration of organic acids. A suitableindicator for the titration is thymol blue. Thymol blue is yellow in acid and blue in alkali. In atitration a solution of an organic acid was added from a burette to a conical flask containing

25.0 cm3 of a barium hydroxide solution and a few drops of thymol blue.

(i) Describe in full the colour change at the end-point of this titration.

...............................................................................................................(1)

12

(ii) Thymol blue is an acid. State how the average titre would change if a few cm3, ratherthan a few drops, of the indicator were used by mistake in this titration.

...............................................................................................................(1)

(iii) Barium hydroxide is toxic. Suggest one safety precaution you would take to minimisethis hazard when wiping up a spillage of barium hydroxide solution.

...............................................................................................................

...............................................................................................................(1)

(iv) Suggest one reason why a 250 cm3 conical flask is preferred to a 250cm3 beaker fora titration.

...............................................................................................................

...............................................................................................................(1)

of 80

(v) Suggest one reason why repeating a titration can improve its reliability

...............................................................................................................

...............................................................................................................(1)

(b) Solubility data for barium hydroxide and calcium hydroxide are given in the table below.

Compound Solubility at 20 °C / g dm–3

barium hydroxide 38.9

calcium hydroxide 1.73

(i) Use the data given in the table to calculate the concentration, in mol dm–3, of asaturated solution of calcium hydroxide (Mr = 74.1) at 20°C.

...............................................................................................................

...............................................................................................................(1)

(ii) Suggest one reason why calcium hydroxide solution is not used in the titration of a

0.200 mol dm–3 solution of an acid.

...............................................................................................................

...............................................................................................................(1)

(Total 7 marks)

In an experiment to determine its solubility in water, solid barium hydroxide was added to 100cm3

of water until there was an excess of the solid. The mixture was filtered and an excess of sulfuricacid was added to the filtrate. The barium sulfate produced was obtained from the reactionmixture, washed with cold water and dried. The mass of barium sulfate was then recorded.

(a) Explain why the mixture was filtered before the addition of sulfuric acid.

........................................................................................................................

........................................................................................................................(1)

13

(b) State how the barium sulfate produced was obtained from the reaction mixture.

........................................................................................................................

........................................................................................................................(1)

of 80

(c) Explain why the barium sulfate was washed before it was dried.

........................................................................................................................

........................................................................................................................(1)

(d) Write an equation for the reaction between barium hydroxide and sulfuric acid.

........................................................................................................................(1)

(e) In an experiment, 4.25 g of barium sulfate were formed when an excess of sulfuric acid

was added to 100 cm3 of a saturated solution of barium hydroxide.

(i) Use data from the Periodic Table to calculate the Mr of barium sulfate.Give your answer to one decimal place.

...............................................................................................................(1)

(ii) Calculate the amount, in moles, of BaSO4 in 4.25 g of barium sulfate.

...............................................................................................................

...............................................................................................................(1)

(iii) Use your answer from part (ii) to calculate the mass of barium hydroxide

(Mr = 171.3) present in 1 dm3 of saturated solution. Show your working.

...............................................................................................................

...............................................................................................................

...............................................................................................................(2)

(f) Barium sulfate is taken by mouth by patients so that an outline of a human digestive systemcan be viewed using X-rays. Explain why patients do not suffer any adverse effects frombarium sulfate when it is known that solutions containing barium ions are toxic.

........................................................................................................................

........................................................................................................................(1)

(Total 9 marks)

of 80

A chemist was asked to prepare a standard solution of sodium carbonate.The chemist dissolved an accurately known mass of sodium carbonate in a small amount of

water in a conical flask. The chemist then poured the solution into a 250 cm3 graduated flask andmade the solution up to the mark. Suggest one improvement to the chemist’s procedure.

.................................................................................................................................

.................................................................................................................................(Total 1 mark)

14

(a) Propanoic acid can be made from propan-1-ol by oxidation using acidified potassiumdichromate(VI). Propanal is formed as an intermediate during this oxidation.

(i) State the colour of the chromium species after the potassium dichromate(VI) hasreacted.

...............................................................................................................(1)

15

(ii) Describe the experimental conditions and the practical method used to ensure thatthe acid is obtained in a high yield. Draw a diagram of the assembled apparatus youwould use.

Conditions .............................................................................................

...............................................................................................................

Apparatus

(4)

(iii) Describe the different experimental conditions necessary to produce propanal in highyield rather than propanoic acid.

...............................................................................................................

...............................................................................................................(2)

of 80

(b) Propan-1-ol is a volatile, flammable liquid.Give one safety precaution that should be used during the reaction to minimise this hazard.

........................................................................................................................(1)

(c) A student followed the progress of the oxidation of propan-1-ol to propanoic acid byextracting the organic compounds from one sample of reaction mixture.

(i) Give a chemical reagent which would enable the student to confirm the presence ofpropanal in the extracted compounds.State what you would observe when propanal reacts with this reagent.

Reagent .............................................................................................

Observation .......................................................................................

............................................................................................................(2)

(ii) Give a chemical reagent that would enable the student to confirm the presence ofpropanoic acid in the extracted compounds.State what you would observe when propanoic acid reacts with this reagent.

Reagent .............................................................................................

Observation .......................................................................................

............................................................................................................(2)

(d) Predict which one of the compounds, propan-1-ol, propanal and propanoic acid will havethe highest boiling point. Explain your answer.

Prediction ....................................................................................................

Explanation ..................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................(3)

(Total 15 marks)

Steel rods are cleaned before they are painted. The rods are cleaned by passing them through abath of dilute sulfuric acid. This process produces large quantities of iron(II) sulfate.

(a) Write an equation for the reaction between iron and dilute sulfuric acid.

........................................................................................................................(1)

16

of 80

(b) State one chemical hazard in this process and suggest an appropriate safety precaution forthis hazard.

Hazard ...........................................................................................................

Precaution .....................................................................................................(2)

(Total 3 marks)

The concentration of iron(III) ions in a dilute solution can be determined by visible spectrometry.The absorption of light of a particular frequency by solutions of iron(III) sulfate of differentconcentrations was measured. The results are shown in the table below.

Percentageabsorbance

Concentration of iron(III)

sulfate / mol dm–3

1.0 7.5 × 10–3

2.5 14.0 × 10–3

5.0 27.5 × 10–3

7.0 37.5 × 10–3

10.0 54.0 × 10–3

12.0 65.0 × 10–3

17

of 80

(a) Use these results to plot a graph of percentage absorbance (y-axis) against concentrationof iron(III) sulfate on the grid below.Draw a straight line of best fit.

(2)

(b) Use your graph to determine the concentration of an iron(III) sulfate solution that has apercentage absorbance of 14.0%.

........................................................................................................................(1)

(Total 3 marks)

(a) State why it is necessary to maintain a constant temperature in an experiment to measurean equilibrium constant.

........................................................................................................................(1)

18

of 80

(b) Suggest one method for maintaining a constant temperature in an experiment.

........................................................................................................................(1)

(Total 2 marks)

Samples of 1-chloropropane and ethanoyl chloride can be distinguished by the addition of anaqueous solution of silver nitrate.State what you would observe with each sample.

Observation with 1-chloropropane

.................................................................................................................................

.................................................................................................................................

Observation with ethanoyl chloride.

.................................................................................................................................

.................................................................................................................................(Total 2 marks)

19

The following pairs of compounds can be distinguished by observing what happens in test-tubereactions.For each pair, give a suitable aqueous reagent that could be added separately to eachcompound.Describe what you would observe in each case.

(a) NaF(aq) and NaCl(aq)

Reagent ......................................................................................................

Observation with NaF(aq) ...........................................................................

Observation with NaCl(aq) ..........................................................................(3)

20

(b) BaCl2(aq) and MgCl2(aq)

Reagent .......................................................................................................

Observation with BaCl2(aq) ..........................................................................

Observation with MgCl2(aq) ..........................................................................(3)

(c) AgCl(s) and AgI(s)

Reagent .......................................................................................................

Observation with AgCl(s) .............................................................................

Observation with AgI(s) ...............................................................................(3)

of 80

(d) Butan-2-ol(l) and 2-methylpropan-2-ol(l)

Reagent …...................................................................................................

Observation with butan-2-ol(l) .....................................................................

Observation with 2-methylpropan-2-ol(l) .....................................................(3)

(Total 12 marks)

Aqueous metal ions can be identified by test-tube reactions.

For each of the following, describe what you would observe.

Write an equation or equations for any reactions that occur.

(a) The addition of aqueous sodium carbonate to a solution containing

[Fe(H2O)6]3+(aq) ions.

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................(4)

21

(b) The addition of aqueous sodium hydroxide, dropwise until in excess, to a solution

containing [Al(H2O)6]3+(aq) ions.

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................(4)

of 80

(c) The addition of dilute aqueous ammonia, dropwise until in excess, to a solution containing

[Cu(H2O)6]2+(aq) ions.

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................(4)

(d) The addition of concentrated hydrochloric acid, dropwise until in excess, to a solution

containing [Cu(H2O)6]2+(aq) ions.

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................(2)

(Total 14 marks)

Ammonium salts such as ammonium nitrate are used in fertilisers. The ammonium nitratecontent of a fertiliser can be determined by heating a sample of the fertiliser with an excess ofsodium hydroxide solution. An equation for this reaction is shown below.

NH4NO3 + NaOH NH3 + NaNO3 + H2O

Heating ensures that all of the ammonia produced is given off as a gas. The unreacted sodiumhydroxide remaining in the solution can be determined by a titration with standard hydrochloricacid.

(a) Explain why it is necessary to remove all of the ammonia before titrating the unreactedsodium hydroxide.

........................................................................................................................

........................................................................................................................(1)

22

of 80

(b) Suggest why it is important to test samples from more than one batch of the fertiliser.

........................................................................................................................

........................................................................................................................(1)

(c) Ammonium nitrate decomposes when heated to form water and one other product.Write an equation for this reaction.

........................................................................................................................(1)

(d) The table below shows some information about three salts that could be used in fertilisers.

SaltNitrogen content

by mass / %Price pertonne / £

Ammonium chloride 26.2 134

Ammonium nitrate 35.0 175

Ammonium sulfate 21.2 111

(i) Use the data in the table to determine the salt that offers the best value for money,based on nitrogen content. Show your working.

...............................................................................................................

...............................................................................................................

...............................................................................................................(2)

(ii) Ammonium nitrate is very soluble in water. Suggest one disadvantage of its highsolubility when ammonium nitrate is used in a fertiliser.

...............................................................................................................

...............................................................................................................(1)

(e) A saturated solution of ammonia contains 300 g of ammonia in 1.00 dm3 of solution.

Calculate the concentration, in mol dm–3, of ammonia in this solution.

........................................................................................................................

........................................................................................................................(1)

(Total 7 marks)

of 80

In an experiment to determine the concentration of a solution of sodium hydroxide, 25.0 cm3 of

0.100 mol dm–3 hydrochloric acid were transferred to a conical flask. An indicator was added tothe flask. The solution of sodium hydroxide was then added to the flask from a burette.

(a) State a suitable amount of indicator solution that should be added to the flask.

........................................................................................................................

........................................................................................................................(1)

23

(b) State why it is important to fill the space below the tap in the burette with alkali beforebeginning the titration.

........................................................................................................................

........................................................................................................................(1)

(Total 2 marks)

An equation for the decomposition of hydrogen peroxide is shown below.

2H2O2 2H2O + O2

State the measurements you would take in order to investigate the rate of this reaction.

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................(Total 2 marks)

24

Ethanol can be oxidised slowly to ethanal. State how a sample of ethanol could be tested toconfirm the presence of ethanal. State what you would observe.

Test .........................................................................................................................

Observation ............................................................................................................(Total 2 marks)

25

of 80

The scheme below shows some reactions of copper(II) ions in aqueous solution.W, X, Y and Z are all copper-containing species.

(a) Identify ion W. Describe its appearance and write an equation for its formation from


Ion W............................................................................................................

Appearance .................................................................................................

Equation …...................................................................................................(3)

26

(b) Identify compound X. Describe its appearance and write an equation for its formation from


Compound X ................................................................................................

Appearance ..................................................................................................

Equation .......................................................................................................(3)

(c) Identify ion Y. Describe its appearance and write an equation for its formation from X.

Ion Y ............................................................................................................

Appearance ..................................................................................................

Equation .......................................................................................................(3)

of 80

(d) Identify compound Z. Describe its appearance and write an equation for its formation from


Compound Z ...............................................................................................

Appearance .................................................................................................

Equation ......................................................................................................(3)

(e) Copper metal can be extracted from a dilute aqueous solution containing copper(II) ionsusing scrap iron.

(i) Write an equation for this reaction and give the colours of the initial and final aqueoussolutions.

Equation .............................................................................................

Initial colour ........................................................................................

Final colour .........................................................................................(3)

(ii) This method of copper extraction uses scrap iron. Give two other reasons why thismethod of copper extraction is more environmentally friendly than reduction of copperoxide by carbon.

Reason 1 ............................................................................................

Reason 2 ............................................................................................(2)

(Total 17 marks)

of 80

Ethanoic acid is manufactured in industry from methanol and carbon monoxide in a multi-stepprocess involving hydrogen iodide. Ethanoic acid is obtained from the reaction mixture byfractional distillation. Methanoic acid is a useful by-product of this process.

The Ka value of an organic acid can be determined by using the pH curve obtained when the acid

is titrated against sodium hydroxide. The pH of the solution formed when exactly half of the acidhas been neutralised is equal to the pKa value of the acid. The Ka value of the acid can be used

to confirm its identity.

A chemist used a pH curve to determine the pKa value of acid Y, formed during the manufacture

of ethanoic acid. The chemist transferred 25.0 cm3 of a solution of acid Y into a beaker using apipette, and measured the pH of the acid solution using a pH meter which could be read to one

decimal place. A solution of sodium hydroxide of concentration 0.100 mol dm–3 was added froma burette in small portions. The pH of the mixture was recorded after each addition of the sodiumhydroxide solution. The chemist’s results are given in the table below.

Volume of sodiumhydroxide solution

added / cm3

pHVolume of sodiumhydroxide solution

added / cm3

pH

0.0 3.0 23.5 5.1

2.0 3.4 24.0 5.5

4.0 3.5 24.5 11.8

8.0 3.7 25.0 12.1

12.0 4.3 26.0 12.3

16.0 4.1 27.0 12.4

20.0 4.3 28.0 12.5

22.0 4.7 30.0 12.5

27

of 80

(a) Use the results given in the table above to plot a graph of pH (y-axis) against volume ofsodium hydroxide solution added. Use the points to draw the pH curve, ignoring anyanomalous results.

(6)

of 80

(b) Use your graph from part (a) to determine the

(i) volume of sodium hydroxide solution at the end-point of the titration

................... cm3

(ii) volume of sodium hydroxide solution needed to neutralise half the acid

................... cm3

(iii) pH of the half-neutralised mixture. Give your answer to one decimal place.

.........................(3)

(c) Use the pH of the half-neutralised mixture from part (b) (iii) to calculate the value of the aciddissociation constant, Ka, of the acid Y. Show your working.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(2)

(d) The table below shows the Ka values for some organic acids.

Acid Ka / mol dm–3

Methanoic acid 1.6 × 10–4

Ethanoic acid 1.7 × 10–5

Iodoethanoic acid 6.8 × 10–4

Propanoic acid 1.3 × 10–5

Use your answer from part (c) to identify acid Y from this table.

........................................................................................................................(1)

of 80

(e) For the pipette and the burette, the maximum total errors are shown below. These errorstake into account multiple measurements.

pipetteburette

± 0.05 cm3

± 0.15 cm3

Estimate the percentage error in using each of these pieces of apparatus. You should useyour answer to part (b) (i) to estimate the percentage error in using the burette.

........................................................................................................................

........................................................................................................................

........................................................................................................................(1)

(f) Calculate the difference between the Ka value from part (c) and the Ka value of the acid you

identified as the acid Y in the table in part (d).

Express this difference as a percentage of the value given in the table in part (d). (If youcould not complete the calculation in part (c), you should assume that the Ka value

determined from the graph is 1.9 × 10–4 mol dm–3. This is not the correct value.)

........................................................................................................................

........................................................................................................................(1)

(g) Other than by using a different pH meter, state one way in which the accuracy of the pHreadings could be improved.

........................................................................................................................

........................................................................................................................(1)

(h) State why there was little change in the pH value of the mixture when between 8 cm3 and

20 cm3 of alkali were added.

........................................................................................................................(1)

(Total 16 marks)

of 80

(a) When a solution containing iron(II) ions is treated with a slight excess of a solutioncontaining ethanedioate ions a bright yellow precipitate of hydrated iron(II) ethanedioate,FeC2O4.2H2O, is formed. The precipitate is filtered off, washed with propanone and thenallowed to dry. A typical yield of the solid is 95%.

(i) Propanone boils at 56 °C and is miscible with water in all proportions. Suggest tworeasons why washing with propanone is an effective method for producing a pure, dryprecipitate.

Reason 1 ..............................................................................................

...............................................................................................................

Reason 2 ..............................................................................................

...............................................................................................................(2)

28

(ii) By suggesting a simple test tube reaction, state how the filtrate could be tested toshow that all of the iron(II) ions have been removed from the solution. State what youwould observe.

Test ......................................................................................................

Observation ..........................................................................................(2)

(iii) Suggest one reason why the typical yield of iron(II) ethanedioate is less than 100%.

...............................................................................................................

...............................................................................................................(1)

(iv) Calculate the mass of hydrated iron(II) ethanedioate, FeC2O4.2H2O that can be

formed from 50.0 cm3 of a 0.50 mol dm–3 solution of iron(II) sulfate when the yield ofthe reaction is 95%. Show your working.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................(3)

of 80

(v) The identity of the precipitate can be confirmed by dissolving it in sulfuric acid andtitrating the mixture with potassium manganate(VII).

Deduce the number of moles of iron(II) ethanedioate that would react with one moleof potassium manganate(VII) in acidic solution.

...............................................................................................................

...............................................................................................................(1)

(b) Ethanedioate ions can be used to remove calcium ions from blood plasma.A precipitate of calcium ethanedioate is formed. Write an ionic equation for the reaction ofethanedioate ions with calcium ions.

........................................................................................................................

........................................................................................................................(1)

(c) Ethanedioic acid is used to clean marble, a form of calcium carbonate. Suggest one reasonwhy the reaction between ethanedioic acid and marble stops after a short time.

........................................................................................................................

........................................................................................................................(1)

(d) Tea leaves contain ethanedioic acid. Suggest one reason why tea drinkers do not sufferfrom ethanedioic acid poisoning.

........................................................................................................................(1)

(e) Ethanedioic acid is produced by the oxidation of carbon monoxide in a multi-step process.The equation which summarises the reactions taking place is shown below.

4CO + 4NaOH + O2 + 4HCl → 2H2C2O4 + 4NaCl + 2H2O

Calculate the percentage atom economy for the formation of ethanedioic acid in thisreaction. Show your working.

........................................................................................................................

........................................................................................................................

........................................................................................................................(2)

(Total 14 marks)

of 80

Hydrogen peroxide is a powerful oxidising agent. Acidified hydrogen peroxide reacts with iodideions to form iodine according to the following equation.

H2O2(aq) + 2H+(aq) + 2I−(aq) → I2(aq) + 2H2O(l)

The initial rate of this reaction is investigated by measuring the time taken to produce sufficientiodine to give a blue colour with starch solution.

A series of experiments was carried out, in which the concentration of iodide ions was varied,while keeping the concentrations of all of the other reagents the same. In each experiment thetime taken (t) for the reaction mixture to turn blue was recorded.

The initial rate of the reaction can be represented as ( ), and the initial concentration of iodideions can be represented by the volume of potassium iodide solution used.

A graph of log10 ( ) on the y-axis against log10 (volume of KI(aq)) is a straight line. The gradientof this straight line is equal to the order of the reaction with respect to iodide ions.

The results obtained are given in the table below. The time taken for each mixture to turn bluewas recorded on a stopclock graduated in seconds.

Expt.Volume of

KI(aq) / cm3

log10 (volume ofKI(aq))

Time / s log10 ( )

1 5 0.70 71 −1.85

2 8 0.90 46 −1.66

3 10 1.00 37 −1.57

4 15 1.18 25 −1.40

5 20 1.30 19 −1.28

6 25 1.40 14 −1.15

29

of 80

(a) Use the results given in the table to plot a graph of log10 ( ) on the y-axis against log10

(volume of KI(aq)).

Draw a straight line of best fit on the graph, ignoring any anomalous points.

(5)

of 80

(b) Determine the gradient of the line you have drawn. Give your answer to two decimalplaces. Show your working.

........................................................................................................................

........................................................................................................................

........................................................................................................................(3)

(c) Deduce the order of reaction with respect to iodide ions.

........................................................................................................................(1)

(d) A student carried out the experiment using a flask on the laboratory bench. Thestudent recorded the time taken for the reaction mixture to turn blue. State one waythis method could be improved, other than by repeating the experiment or byimproving the precision of time or volume measurements. Explain why the accuracyof the experiment would be improved.

Improvement .................................................................................................

........................................................................................................................

Explanation ....................................................................................................

........................................................................................................................(2)

(Total 11 marks)

Pure hydrogen peroxide is a colourless liquid with a boiling point of 150 °C. Hydrogen peroxidewas originally produced commercially in a two-stage process. In the first stage barium washeated in air to form barium peroxide. In the second stage barium peroxide was added toaqueous nitric acid. The equations for the reactions are shown below.

Stage 1 Ba(s) + O2(g) BaO2(s)

Stage 2 BaO2(s) + 2HNO3(aq) H2O2(aq) + Ba(NO 3)2(aq)12

30

(a) Suggest one method of separating hydrogen peroxide from the reaction mixture inStage 2.

........................................................................................................................

........................................................................................................................(1)

(b) Apart from cost, suggest one reason why nitric acid was eventually replaced bysulfuric acid in Stage 2.

........................................................................................................................

........................................................................................................................(1)

of 80

(c) Suggest one reason why infrared spectroscopy could not be used to indicate thepresence of a small amount of water in hydrogen peroxide.

........................................................................................................................

........................................................................................................................(1)

(Total 3 marks)

Ethanal is prepared by heating ethanol with potassium dichromate(VI) in the presence of sulfuricacid. Figures 1 and 2 show two possible ways of heating this reaction mixture.

Figure 1 Figure 2

State which arrangement would not be suitable for the preparation of ethanal. Explain youranswer.

Arrangement ...........................................................................................................

Explanation .............................................................................................................

.................................................................................................................................(Total 2 marks)

31

of 80

Describe briefly how you would ensure that a reading from a pH meter is accurate.

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................(Total 2 marks)

32

Describe briefly how you could measure the melting point of aspirin.

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................(Total 2 marks)

33

Some antacid tablets contain sodium hydrogencarbonate, sucrose and citric acid.

(a) Analysis of a pure sample of citric acid showed that it contained 37.50% of carbon and4.17% of hydrogen by mass, the remainder being oxygen. Use these data to show that theempirical formula of the acid is C6H8O7.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(3)

34

(b) When the antacid tablet is added to water, sodium hydrogencarbonate and citric acid reacttogether to form a gas. Identify this gas.

........................................................................................................................(1)

of 80

(c) A weighed portion of this antacid was added to water. The gas formed was collected and itsvolume measured.

(i) Draw a diagram to show how this experiment could have been carried out to collectand measure the volume of the gas.

(ii) The experiment was repeated with further weighed portions of the same antacid.

The results are shown below.

Experiment 1 2 3 4 5

Mass of antacid / g 2.60 1.17 0.88 2.31 1.80

Volume of gas collected / cm3 168 86 57 149 116

of 80

1 On the graph paper below, plot a graph of mass of antacid (x-axis) againstvolume of gas collected.

(3)

2 Draw a line of best fit on the graph, ignoring any anomalous points.(1)

of 80

3 Use the graph to determine the volume of gas which would have been collectedusing 2.00 g of antacid.

Volume of gas collected .......................................(1)

(d) Suggest one reason why the presence of sodium hydrogencarbonate in the stomach maycause a person to suffer some extra discomfort for a short time.

........................................................................................................................(1)

(e) Explain why the value for the Mr of citric acid does not need to be an exact value to deducethe molecular formula of citric acid from its empirical formula.

........................................................................................................................

........................................................................................................................(2)

(f) Apart from misreading the gas volume, suggest two reasons why the volumes of gascollected may be lower than the volumes of gas produced.

Reason 1 .......................................................................................................

........................................................................................................................

Reason 2 .......................................................................................................

........................................................................................................................(2)

(g) Explain why it is important to record the temperature and pressure when measuring thevolume of a gas.

........................................................................................................................

........................................................................................................................(1)

(h) Suggest why, in an analysis of an antacid, it is important to test samples from more thanone bottle of the antacid.

........................................................................................................................

........................................................................................................................(1)

of 80

(i) In the industrial production of sodium hydrogencarbonate, ammonia and carbon dioxide arebubbled through a saturated solution of sodium chloride. The equation for this reaction, andsome solubility data, are shown below.

NaCl(aq) + NH3(aq) + CO2(g) + H2O(l) → NaHCO3(s) + NH4Cl(aq)

Compound Solubility in water at 20 °C / g dm–3

sodium chloride 360

sodium hydrogencarbonate 96

ammonium chloride 370

(i) Suggest one reason why sodium hydrogencarbonate precipitates from the reactionmixture at this temperature.

...............................................................................................................(1)

(ii) Explain how this reaction could be used to remove carbon dioxide from the gasesformed when fossil fuels are burned.

...............................................................................................................

...............................................................................................................(1)

(j) The thermal decomposition of sodium hydrogencarbonate produces sodium carbonate.The other products are water and carbon dioxide. Write an equation for this thermaldecomposition.

........................................................................................................................(1)

(k) Sodium carbonate is produced on an industrial scale by a multi-step process. The equationwhich summarises the reactions taking place is shown below.

CaCO3 + 2NaCl → CaCl2 + Na2CO3

Calculate the percentage atom economy for the production of sodium carbonate by thisreaction.

........................................................................................................................(1)

(Total 20 marks)

of 80

A chemical company’s records refer to the following acids

hydrochloric acidhydrobromic acidhydriodic acid

nitric acidsulfuric acid

A waste tank was thought to contain a mixture of two of these acids. A chemist performedtest-tube reactions on separate samples from the waste tank. The results of these tests areshown below.

Test Reagent Observations

A Barium chloride solution White precipitate

B Silver nitrate solution White precipitate

35

(a) Use the result from Test A to identify an acid in the company’s records which must bepresent in the waste tank.

........................................................................................................................(1)

(b) Use the results from Test A and Test B to identify an acid in the company’s records whichmust be absent from the waste tank.

........................................................................................................................(1)

(c) The chemist suspected that the waste tank contained hydrochloric acid. State how theprecipitate formed in Test B could be tested to confirm the presence of hydrochloric acid inthe waste tank. State what you would observe.

Test ................................................................................................................

........................................................................................................................

Observation ...................................................................................................

........................................................................................................................(2)

(d) Suggest one reason why carbonate ions could not be present in the waste tank.

........................................................................................................................(1)

(Total 5 marks)

of 80

Magnesium carbonate, MgCO3, can occur as the anhydrous compound, or as hydrates with 2, 3or 5 molecules of water of crystallisation. All types of magnesium carbonate can be decomposedto form magnesium oxide, an important starting material for many processes. This decompositionreaction can be used to identify the type of magnesium carbonate present in a mineral.

A chemist was asked to identify the type of magnesium carbonate present in a mineral importedfrom France. The chemist weighed a clean dry crucible, and transferred 0.25 g of the magnesiumcarbonate mineral to the crucible. The crucible was then heated for a few minutes. The cruciblewas then allowed to cool, and the crucible and its contents were reweighed. This process wasrepeated until the crucible and its contents had reached constant mass. The mass of the crucibleand its contents was then recorded.

36

The experiment was repeated using different masses of the magnesium carbonate mineral.

For each experiment the chemist recorded the original mass of the mineral and the mass ofmagnesium oxide left after heating to constant mass. The chemist’s results are shown in thetable below.

Experiment 1 2 3 4 5 6

Mass of mineral / g 1.60 1.17 0.74 1.31 1.80 1.34

Mass of magnesium oxide / g 0.54 0.39 0.24 0.44 0.61 0.49

of 80

(a) Plot a graph of the mass of the mineral (x-axis) against the mass of magnesium oxide onthe grid below.

Draw a straight line of best fit on your graph.

(4)

(b) Use the graph to determine the mass of the mineral which would have formed 0.50 g ofmagnesium oxide.

Mass of the mineral .......................................................................................(1)

of 80

(c) Calculate the amount, in moles, of MgO present in 0.50 g of magnesium oxide.

........................................................................................................................

........................................................................................................................(1)

(d) Use your answers from part (b) and from part (c) to calculate the Mr of the magnesiumcarbonate present in the mineral.

........................................................................................................................

........................................................................................................................

........................................................................................................................(1)

(e) Use your answer from part (d) to confirm that this mineral is MgCO3.2H2O

(If you could not complete the calculation in part (d), you should assume that theexperimental Mr value is 122.0 This is not the correct answer.)

........................................................................................................................

........................................................................................................................

........................................................................................................................(1)

(f) Explain why it was not necessary to use a more precise balance in this experiment.

........................................................................................................................

........................................................................................................................(1)

(g) Consider your graph and comment on the results obtained by the chemist. Identify anyanomalous results.

Comment .......................................................................................................

........................................................................................................................

Anomalous results .........................................................................................

........................................................................................................................(2)

(h) Explain why it was necessary for the chemist to heat the crucible and its contents toconstant mass.

........................................................................................................................(1)

of 80

(i) Suggest one reason in each case why

(i) small amounts of the mineral, such as 0.10 g, should not be used in this experiment.

...............................................................................................................

...............................................................................................................(1)

(ii) large amounts of the mineral, such as 50 g, should not be used in this experiment.

...............................................................................................................

...............................................................................................................(1)

(j) Analysis of a different hydrated magnesium carbonate showed that it contained 39.05% bymass of water. Determine the formula of this hydrated magnesium carbonate.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(2)

(k) Magnesium oxide is produced by the thermal decomposition of magnesium carbonate andby the thermal decomposition of magnesium hydroxide. The equations for the reactionstaking place are shown below.

Reaction 1Reaction 2

MgCO3

Mg(OH)2

→→

MgO + CO2

MgO + H2O

Show that Reaction 2 has the greater atom economy for the production of magnesiumoxide.

........................................................................................................................

........................................................................................................................(2)

(l) Apart from cost, suggest one advantage of using magnesium hydroxide rather thanmagnesium carbonate to reduce acidity in the stomach.

........................................................................................................................

........................................................................................................................(1)

(Total 19 marks)

of 80

In an experiment to determine the rate of a reaction, the volume of gas produced in the reactionwas measured at regular intervals for several minutes.

(a) State one experimental condition that must be kept constant during the experiment.

........................................................................................................................

........................................................................................................................(1)

37

(b) Describe how the initial rate of this reaction can be determined from a graph of volume ofgas produced against time.

........................................................................................................................

........................................................................................................................(1)

(Total 2 marks)

Both strontium carbonate and strontium sulfate are white solids which are insoluble in water.Strontium carbonate reacts with hydrochloric acid to produce a solution of strontium chloride.Strontium sulfate does not react with hydrochloric acid.

Describe how you would obtain strontium sulfate from a mixture of strontium carbonate andstrontium sulfate.

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................(Total 2 marks)

38

In an investigation of the chemical properties of alcohols, a mixture of ethanol and acidifiedpotassium dichromate(VI) is heated in a conical flask in a water bath.

(a) Explain why a water bath is used to heat the mixture.

........................................................................................................................

........................................................................................................................(1)

39

(b) Describe the colour change which would be observed.

........................................................................................................................

........................................................................................................................(1)

(Total 2 marks)

of 80

A chemist has discovered that the labels have fallen off four bottles each of which contains adifferent organic liquid. These liquids are known to be propan-2-ol, propanal, hexene and1-bromopropane.

Suggest a series of test-tube reactions which a chemist could use to confirm the identities of thefour compounds. State the reagents used and the observations expected.

(Total 10 marks)

40

(a) When aqueous ammonia was added to an aqueous solution of cobalt(II) sulfate, a blueprecipitate M was formed. Identify the cobalt-containing species present in aqueouscobalt(II) sulphate and in the precipitate M.

Cobalt-containing species ..........................................................................

Precipitate M ...............................................................................................(2)

41

(b) Precipitate M dissolved when an excess of concentrated aqueous ammonia was added.The solution formed was pale brown due to the presence of the cobalt-containing speciesP. Identify P.

......................................................................................................................(1)

(c) On standing in air, the colour of the solution containing P slowly darkened as the cobalt-containing species Q was formed. State the type of reaction occurring when P changes intoQ and identify the reactant responsible for this change.

Type of reaction ..........................................................................................

Reactant responsible ...................................................................................(2)

(d) When potassium iodide was added to the solution containing Q and the mixture wasacidified, a dark brown solution due to the presence of R was formed. On addition of starchsolution the mixture turned blue-black.

Identify R and explain its formation.

Identity of R .................................................................................................

Explanation ..................................................................................................(2)

(Total 7 marks)

of 80

(a) State the trend in the boiling points of the halogens from fluorine to iodine and explainthis trend.

Trend ............................................................................................................

Explanation ...................................................................................................

......................................................................................................................

......................................................................................................................(4)

42

(b) Each of the following reactions may be used to identify bromide ions. For each reaction,state what you would observe and, where indicated, write an appropriate equation.

(i) The reaction of aqueous bromide ions with chlorine gas

Observation ........................................................................................

Equation ..............................................................................................

(ii) The reaction of aqueous bromide ions with aqueous silver nitrate followed bythe addition of concentrated aqueous ammonia

Observation with aqueous silver nitrate ...............................................

Equation ..............................................................................................

Observation with concentrated aqueous ammonia ..............................

.............................................................................................................

(iii) The reaction of solid potassium bromide with concentrated sulphuric acid

Observation 1 .....................................................................................

Observation 2 .....................................................................................(7)

(c) Write an equation for the redox reaction that occurs when potassium bromide reactswith concentrated sulphuric acid.

......................................................................................................................(2)

(Total 13 marks)

of 80

Mark schemes

(a) To prevent vigorous boiling / uneven boiling / bubbling vigorously

Reference to an effect on ‘reaction’ here loses this mark.1

1

(b) Condenser

Accept ‘condensation chamber’ or ‘condensation tube’.1

Should show effective water jacket and central tube

If a flask is also drawn then the condenser must be at anappropriate angle.

Apparatus must clearly work.

Ignore direction of water flow.

Diagram must have a clear flow of vapour and water eg unblockedcentral tube or flow indicated by arrows.

1[3]

(Mix the alcohol with warm) K2Cr2O7 / H+ allows 3° identification by lack of reaction

Scheme must allow the alcohol to be distinguished to get all marks.1

2

Distillation of initial product needed for 1° / 2°

If distillation stage not clear then max. 2 (M1 and M3).

Awareness of correct reactions / lack of reaction relating to eachclass of alcohol is worth 1 mark.

1

Effect of Tollens’ / Fehling’s on oxidation product to identify 1° or 2° (by default)

Reacting Tollens’ / Fehling’s with alcohols directly is incorrect andgains no M2 or M3.

Detailed observations relating to the reactions are not needed butshould be penalised where incorrect.

1[3]

(a) For reactions 1 to 3 must show complex ions as reactants and products

Take care to look for possible identification on flow chart

Reaction 1

ammonia solution1

3

W is [Co(NH3)6]2+

1

[Co(H2O)6]2+ + 6NH3 → [Co(NH3)6]2+ + 6H2O

Correct equation scores all 3 marks1

of 80

Reaction 2

Allow oxygen, Do not allow air

H2O2

1

X is [Co(NH3)6]3+

1

2[Co(NH3)6]2+ + H2O2 → 2[Co(NH3)6]3+ + 2OH–

Allow 2[Co(NH3)6]2+ + ½O2 + H2O → 2[Co(NH3)6]3+ + 2OH–

Correct equations score all 3 marks1

Reaction 3

HCl

Do not allow Cl– but mark on1

Y is [CoCl4]2-

1

[Co(H2O)6]2+ + 4Cl– → [CoCl4]2- + 6H2O/

Correct equation scores previous mark

[Co(H2O)6]2+ + 4HCl → [CoCl4]2- + 6H2O + 4H+

This equation scores all three marks1

Reaction 4

Na2CO3 Or NaOH/NH3

Do not allow CaCO3 as a reagent but mark on1

Z is CoCO3 Co(OH)2/Co(H2O)4(OH)2

1

[Co(H2O)6]2+ + CO32- → CoCO3 + 6H2O [Co(H2O)6]2++ 2OH–→

Co(H2O)4(OH)2+ 2H2O etc

Allow waters to stay co-ordinated to Co. This mark also previousmark

Or [Co(H2O)6]2+ + Na2CO3 → CoCO3 + 6H2O + 2Na+

Allow Co2+ + CO32- → CoCO3

1

of 80

(b) SO32- + ½O2 → SO4

2-

Allow multiples1

The activation energy is lower (for the catalysed route)

Or Co3+ attracts SO32-/Co2+ attracts SO3

2-/oppositely charged ionsattract

1

½O2 + 2Co2+ + 2H+ → H2O + 2Co3+

1

2Co3+ + SO32- + H2O → 2Co2+ + SO4

2- + 2H+

Allow these equations in either order1

[16]

Minimum volume and hot water:

Note that this question is worth a total of 5 marks.

Any two from:

to obtain saturated solution

to increase yield / reduce amount left in solution

enable crystallisation (on cooling)

Do not allow ‘because acid doesn’t dissolve well in cold water’.Max 2

4

Filtered hot: to remove insoluble impurities / to prevent crystals forming during filtration1

Cooled in ice: to increase amount of crystals that are formed

Do not allow ‘to cool quickly’.1

Washed with cold water: to remove soluble impurities

Allow ‘washing with hot water would dissolve some of the crystals’.1

[5]

(a) Mg + 2C6H4(OH)COOH → (C6H4(OH)COO)2Mg + H2

Accept multiples, including fractions.1

5

of 80

(b) Gas syringe / inverted burette over water / measuring cylinder over water

Collection apparatus must show graduations or be clearly labelled(eg syringe, burette, measuring cylinder).

1[2]

(a) To reduce any Fe3+ ions to Fe2+ ions

Allow ‘to ensure that all of the iron present is in the form of Fe 2+

ions’ or ‘to ensure that no Fe 3+ ions are present’.1

6

(b) Zinc would react with MnO4− / Fe3+ produced in titration

Do not allow ‘would increase titre value’.

Do not allow ‘zinc would react’ without further qualification.1

[2]

(a) (i) Flask with side arm17

Buchner funnel and horizontal filter paper

Allow Hirsch funnel and horizontal filter paper.

Do not allow standard Y-shaped funnel.

If there is not a clear air-tight seal (labelled or drawn) between thefunnel and the flask maximum 1 mark.

1

(ii) Mr KMnO4 = 158(.0)1

Mass = 0.225 × 158 / 3 = 11.9 (g)

Lose M2 if no working shown.

Allow consequential mark on an incorrect Mr for KMnO4

1

Precision mark: three significant figures

Allow if mass incorrect.1

(iii) (Unpleasant) taste

Ignore smell.1

(b) Difficult to see meniscus / line on graduated flask

Do not allow reference to over filling.1

[7]

(a) Stop the formation of MnO2 / Ensures all MnO4– reacts to form Mn2+ / becomes colourless

18

(b) Weak acid / Does not supply sufficient H+

1

of 80

(c) It is self-indicating / Purple to colourless end-point or vice versa

If colours mentioned they must be correct.1

[3]

(a) Melting range would be wide (>3 deg C) / not sharp

Allow melts over a range of temperatures.1

9

below / before the true m.p.

Do not allow ‘above or below’.1

(b) Temperature on thermometer not the same as the sample

Allow sample heats up at a different / higher / lower rate thanthermometer.

1[3]

(a) (i) M1 (yellow precipitate is) silver iodide OR AgI (whichmay be awarded from the equation)

M2 Ag+ + I– → AgI (Also scores M1 unless contradicted)

M3 sodium chloride OR NaCl

For M2

Accept multiples

Ignore state symbols

Allow crossed out nitrate ions, but penalise if not crossed out3

10

(ii) The silver nitrate is acidified to

• react with / remove ions that would interfere with the test

• prevent the formation of other silver precipitates / insoluble silver compoundsthat would interfere with the test

• remove (other) ions that react with the silver nitrate

• react with / remove carbonate / hydroxide / sulfite (ions)

Ignore reference to “false positive”1

of 80

(iii) M1 and M2 in either order

M1 Fluoride (ion) OR F�

M2 • Silver fluoride / AgF is soluble / dissolves (in water)

• no precipitate would form / no visible /observable change

Do not penalise the spelling “fluoride”,

Penalise “fluride” once only

Mark M1 and M2 independently2

(b) M1 Ba2+ + SO42- → BaSO4

(or the ions together)

M2 white precipitate / white solid / white suspension

M3 Barium meal or ( internal ) X-ray or to block X-rays

M4 BaSO4 / barium sulfate is insoluble (and therefore not toxic)

For M1, ignore state symbols

Allow crossed out sodium ions, but penalise if not crossed out

For M2, ignore “milky”

If BaSO3 OR BaS used in M1 and M4, penalise once only

For M3 Ignore radio-tracing

For M4 NOT barium ions

NOT barium

NOT barium meal

NOT “It” unless clearly BaSO4

4

(c) M1 2(12.00000) + 4(1.00794) = 28.03176

M2 Ethene and CO or “they” have an imprecise Mr of 28.0 / 28

OR

Ethene and CO or “they” have the same Mr to one d.p.

OR

These may be shown by two clear, simple sums identifyingboth compounds

of 80

M3 C2H4 + 2O2 → 2CO + 2H2O

(H2C=CH2)

M4 Displayed formula

M5 Type of polymer = Addition (polymer)

M1 must show working using 5 d.p.for hydrogen

Penalise “similar” or “close to”, if this refers to the imprecise valuein M2, since this does not mean “the same”

For M3, accept CH2=CH2 OR CH2CH2

For M4, all bonds must be drawn out including those on either sideof the unit.

Penalise “sticks”

Ignore brackets around correct repeating unit but penalise “n”

Penalise “additional”5

[15]

(a) Hydrochloric acid = C111

Barium chloride = A1

(b) Barium sulfate is insoluble1

CuSO4 + BaCl2 → BaSO4 + CuCl2

Accept multiples.

Accept ionic equation.

Do not penalise lack of state symbols, but if used they must becorrect.

1

(c) CO2 / Carbon dioxide1

(d) Reagent 1 silver nitrate (solution)

Ignore lack of reference to acidifying prior to addition of silver nitratesolution.

1

of 80

Observation 1 White precipitate1

Reagent 2 (dilute) ammonia solution / aqueous ammonia

Do not accept addition of ammonia only.1

Observation 2 (Colourless) solution

Allow ppt dissolves.

Do not allow ‘goes colourless’ or ‘goes clear’.

Chlorine and no visible change or solution does not

become orange scores M3 and M4.1

(e) Gloves / wash hands after use

Ignore ‘eye protection’.

Do not accept ‘do not ingest the chemicals’, ‘wipe up spillages’, ‘usea fume cupboard’, ‘wear a lab coat’ (list principle).

1[10]

(a) (i) Blue to green

Accept blue to yellow.1

12

(ii) Decrease / less acid needed

Ignore references to rate1

(iii) Gloves or avoid skin contact

Allow ‘if reagent contacts skin wash off (immediately)’ or answers tothat effect.

Do not accept ‘wash’ only.

Ignore ‘eye protection’ or ‘lab coat’ or ‘use of fume cupboard’ or‘don’t ingest’.

1

(iv) Less chance of losing liquid on swirling / liquid doesn’t splash on swirling

Do not accept ‘easier to swirl’ on its own.

Do not accept ‘easier to stir’.1

(v) Idea that a single titration could be flawed / anomalous

Allow an indication that the first titration is a rough titration.

Do not allow ‘to improve accuracy’ without qualification.

Do not allow vague references to ‘outliers’.1

(b) (i) 2.3(3) × 10–2

Do not penalise additional significant figures, but do not allow 0.021

of 80

(ii) Dilution of acid needed / may react with carbon dioxide in air

Accept ‘poor end-point’ or ‘no suitable indicator’ or ‘a large volume(of calcium hydroxide) will be needed’.

Ignore references to low solubility or concentration too low.1

[7]

(a) Remove undissolved barium hydroxide / excess solid

Do not accept ‘remove impurities’.1

13

(b) Filtration

Do not accept ‘decanting’ or ‘sieving’.

Ignore references to heating or drying.1

(c) Remove (excess) sulfuric acid1

(d) Ba(OH)2 + H2SO4 → BaSO4 + 2H2O

Accept multiples.

Accept Ba2+ + SO42- → BaSO4

Ignore state symbols.1

(e) (i) 233.4

Accept 2331

(ii) 0.018(2)

Do not penalise additional significant figures, but do not allow 0.02

Allow consequential answer from (i).1

(iii) 0.018(2) × 171.3 = 3.12

Do not penalise precision.

If 0.018 used, answer = 3.081

× 10 = 31.2


Allow this mark if 0.18(2) used directly.

Correct answer without working scores one mark only.

Allow consequential answer on (ii)1

(f) Barium sulfate / it is insoluble

Do not accept answers based on small amount ingested.

Do not accept barium.1

[9]

of 80

Include washings or words to that effect / mix contents

Accept ‘use distilled / deionised water’.

Allow ‘weigh directly into flask’ if washing included.1

[1]

14

(a) (i) Green

Ignore shades of green.1

15

(ii) Excess acidified potassium dichromate(VI)1

Reflux (for some time)1

In the diagram credit should be given for• a vertical condenser

Lose M3 and M4 for a distillation apparatus.1

• an apparatus which would clearly work

Do not allow this mark for a flask drawn on its own.

Penalise diagrams where the apparatus is sealed.1

(iii) Distillation1

Immediately (the reagents are mixed)1

(b) Keep away from naked flames

Allow heat with water-bath or heating mantle.

If a list is given ignore eye protection, otherwise lose this mark.1

(c) (i) Tollens’ or Fehling’s reagents

Incorrect reagent(s) loses both marks.

Accept mis-spellings if meaning is clear.1

Silver mirror / red ppt. formed

Accept ‘blue to red’ but not ‘red’ alone.1

(ii) Sodium carbonate (solution) / Group II metal

Allow indicator solutions with appropriate colours.

Accept any named carbonate or hydrogen carbonate.1

of 80

Effervescence / evolves a gas

Accept ‘fizzes’.1

(d) Propanoic acid

If this mark is lost allow one mark if there is reference to strongerintermolecular forces in the named compound.

Lose M1 and M3.1

Contains hydrogen bonding1

Some comparison with other compounds explaining that the intermolecular forces arestronger in propanoic acid

1[15]

(a) Fe + H2SO4 → FeSO4 + H2

Accept multiples.

Ignore state symbols, even if incorrect.1

16

(b) Hazard acid corrosive or hydrogen flammable / explosive

Accept ‘iron(II) sulfate / sulfuric acid an irritant’.1

Precaution gloves or eye protection or avoid naked flames / spark

Allow ‘if reagent contacts skin wash off immediately’ or answers tothat effect instead of gloves.

Do not allow ‘wipe up spillages’.

Ignore ‘lab coat’ or ‘use of fume cupboard’ or ‘do not ingestchemicals’.

1[3]

(a) Plots all of the points correctly ± one square117

Straight line through the points is best fit

Candidate does not have to extrapolate line to the origin.

Line must pass through the origin ± 1 square.

Lose this mark if the candidate’s line is doubled or kinked.

Allow line that doesn’t pass through the origin if one or more pointsare misplotted.

1

of 80

(b) 7.6 ± 0.1 × 10-2 (mol dm-3)

Do not penalise precision, but at least 2 significant figures.1

[3]

(a) Kc / Ka / equilibrium constant / constant is temperature dependent

Do not allow ‘affects or shifts equilibrium’.1

18

(b) Thermostat / water bath1

[2]

1-chloropropane no visible change

Accept ‘small amount of precipitate’ or ‘precipitate forms slowly’.1

19

ethanoyl chloride white precipitate

Accept ‘large amount of precipitate’ or ‘precipitate formsimmediately’.

1[2]

(a) M1 AgNO3 OR silver nitrate OR any soluble silver salt

M2 remains colourless or no reaction or no (observed)change or no precipitate

M3 white precipitate or white solid/white suspension

An insoluble silver salt OR Tollens’ OR ammoniacal silver nitrate orHCl/AgNO3 is CE = 0 for the clip

For M1

Credit acidified (or HNO3) silver nitrate for M1 and mark on

If silver ions or incorrect formula for silver nitrate, penalise M1 butmark M2 and M3

If no reagent or incorrect reagent in M1, then no marks for M2 orM3

For M2

Ignore “nothing”

Ignore “no observation”

Ignore “clear”

Ignore “dissolves”

For M3

Ignore “cloudy solution” OR “suspension”3

20

of 80

(b) M1 any soluble sulfate by name or formula e.g. sodium sulfateor sulfuric acid.


M3 remains colourless or no reaction or no (observed) changeor no precipitate

OR as an alternative

M1 NaOH/KOH

M2 remains colourless or no reaction or no (observed) change


An insoluble sulfate OR conc H2SO4 is CE = 0 for the clip


For the M1 soluble sulfate

If sulfate ions or incorrect formula for the chosen sulfate, penaliseM1 but mark M2 and M3

For the M1 NaOH/KOH

If ammonia, then CE = 0

If hydroxide ions or incorrect formula for the chosen hydroxide,penalise M1 but mark M2 and M3

For no (observed) change in both alternatives



Ignore “clear”

Ignore “dissolves”

For the white precipitate in both alternatives

Ignore “cloudy solution” OR “suspension”3

(c) M1 ammonia (can be dilute or concentrated)

M2 dissolves OR soluble OR (forms a) colourlesssolution OR goes colourless

M3 does not dissolve OR not soluble OR remains as a solidOR no (observed) change OR no reaction OR yellow solid remains

OR if concentrated ammonia has been used, accept yellowsolid turns white.

of 80

OR as an alternative using conc sulfuric acid

M1 concentrated sulfuric acid OR c(onc) H2SO4

M2 misty/white fumes/gas

OR remains white

OR no change (in colour)

M3 turns black (solid)

OR purple fumes/gas

OR correct reference to H2S observation (e.g. bad egg smell)

For M1

If incorrect formula or “ammonium”, penalise M1 but mark M2 andM3


For M3



For the alternative using sulfuric acid

If dilute sulfuric acid or “aq” (alone) or the idea of concentrated notincluded CE = 0

If incorrect formula, penalise M1 but mark M2 and M3


3

(d) M1 acidified potassium dichromate or K2Cr2O7/H2SO4

OR K2Cr2O7/H+ OR acidified K2Cr2O7

M2 (orange to) green solution OR goes green

M3 (solution) remains orange or no reaction or no (observed) change

Alternative using KMnO4/H2SO4

M1 acidified potassium manganate(VII) or KMnO4/H2SO4

of 80

OR KMnO4/H+ OR acidified KMnO4

M2 colourless solution OR goes colourless

M3 (solution) remains purple or no reaction or no (observed) change


For M1

If “dichromate” or “dichromate(IV)” or incorrect formula or no acid,penalise M1 but mark M2 and M3

For M2 ignore dichromate described as “yellow” or “red”

For M3



For M1

If “manganate” or “manganate(IV)” or incorrect formula or no acid,penalise M1 but mark M2 and M3

Credit alkaline KMnO4 for possible full marks but M2 gives brownprecipitate or solution goes green

3[12]

(a) Brown ppt/solid1

Gas evolved/effervescence1

2[Fe(H2O)6]3+ + 3CO32– → 2Fe(H2O)3(OH)3 + 3CO2 + 3H2O

Must be stated, Allow CO2 evolved. Do not allow CO2 alone

Correct iron product (1) allow Fe(OH)3 and in equation

Balanced equation (1)2

21

of 80

(b) White ppt/solid1

Colourless Solution

Only award M2 if M1 given or initial ppt mentioned1

[Al(H2O)6]3+ + 3OH– → Al(H2O)3(OH)3 + 3H2O

Allow [Al(H2O)6]3+ + 3OH– → Al(OH)3 + 6H2O1

Al(H2O)3(OH)3 + 3OH– → [Al(OH)6]3– + 3H2O

Allow formation of [Al(H2O)6–x(OH)x](x–3)– where x = 4,5,6

Allow product without water ligands

Allow formation of correct product from [Al(H2O)6]3+

1

(c) Blue ppt/solid1

(Dissolves to give a) deep blue solution

Only award M2 if M1 given or initial ppt mentioned1

[Cu(H2O)6]2+ + 2NH3 → Cu(H2O)4(OH)2 + 2NH4+

Allow [Cu(H2O)6]2+ + 2NH3 → Cu(OH)2 + 2NH4+ + 4H2O

Allow two equations: NH3 + H2O → NH4+ + OH–

then [Cu(H2O)6]2+ + 2OH– → Cu(OH)2 + 4H2O etc1

Cu(H2O)4(OH)2 + 4NH3 → [Cu(H2O)2(NH3)4]2+ + 2OH– + 2H2O

Allow [Cu(H2O)6]2+ + 4NH3 → [Cu(H2O)2(NH3)4]2+ + 4H2O1

(d) Green/yellow solution1

[Cu(H2O)6]2+ + 4Cl– → [CuCl4]2– + 6H2O1

[14]

(a) Ammonia is an alkali / would react with HCl

Do not allow ‘fair test’ or ‘to improve accuracy’ without furtherqualification

1

22

of 80

(b) Batches may vary / batch might be contaminated

Do not allow ‘fair test’, ‘to improve accuracy’, ‘reliable’ or‘reproducible’ without further qualification

1

(c) NH4NO3 → N2O + 2H2O

Accept multiples1

(d) (i) ammonium chloride 134 / 26.2 = 5.11 £ per %

ammonium nitrate 175 / 35 = 5.00 £ per %

ammonium sulphate 111 / 21.2 = 5.24 £ per %

Must have some evidence of working to score this markAccept calculations of nitrogen content per pound

1

ammonium nitrate

Accept name or correct formulaAllow consequential answer from candidate’s results

1

(ii) Washed / dissolved / leached from soil by rainwater / eutrophication

Allow root damage due to temperature drop when salt dissolves1

(e) 17.6

Ignore precision of answerIgnore unitsDo not allow 18

1[7]

(a) 2-6 drops / 0.1-0.3 cm3

Accept ‘a few drops’1

23

(b) Incorrect volume recorded / space will fill during titration / produces larger titre value

Do not accept ‘to give an accurate result’ without furtherqualificationDo not accept references to contamination

1[2]

Measure volume of gas / mass loss

If ‘measure concentration’ must explain how to score mark1

24

of 80

At (regular) time intervals

Ignore references to temperatureAccept ‘against time’Do not accept ‘with time’ or ‘over time’ on its own

1[2]

Add Tollens / Fehling’s / Benedict’s reagent / ir spectra

Accept any other chemically correct reagent and observation1

25

Silver mirror / blue to red OR red precipitate (with ethanal) / peak at 1700 cm–1 (in ethanal)

Must have correct test to access second markAccept ‘silver’. Do not accept ‘silver solution’Give one mark for ‘silver mirror test’ and ‘silver mirror’Accept correct answer based on n.m.r. spectra

1[2]

(a) W is CuCl42–

1

Yellow-green/yellow/green

Not necessary to indicate solutionDo not allow precipitate/solid

1

[Cu(H2O)6]2+ + 4Cl– → CuCl42– + 6H2O

Allow + 4HCl → 4H+

1

26

(b) X is Cu(H2O)4(OH)2

Allow Cu(OH)2/copper hydroxide1

Blue precipitate/solid

Ignore shades1

[Cu(H2O)6]2+ + 2NH3 → Cu(H2O)4(OH)2 + 2NH4+

Allow any balanced equation/equations leading to this hydroxide orCu(OH)2

But must use ammonia1

of 80

(c) Y is [Cu(NH3)4(H2O)2]2+

1

Deep/dark/royal blue solution

QoL1

Cu(H2O)4(OH)2 + 4NH3 → [Cu(NH3)4(H2O)2]2+ + 2H2O + 2OH–

Accept equation for formation from Cu(OH)2

1

(d) Z is CuCO3

Allow copper carbonate1

Green solid/precipitate

Allow blue-green precipitate1

[Cu(H2O)6]2+ + CO32– → CuCO3 + 6H2O

1

(e) (i) Cu2+(aq) + Fe(s) → Cu(s) + Fe2+(aq)

Allow hydrated ionsState symbols not essential but penalise if wrong

1

Blue

Do not allow description of solids1

Green

Allow yellow/(red-)brown/orange1

(ii) Any two correct points about copper extraction from twoof these three categories:

Any relevant mention of lower energy consumption

Do not allow reference to electricity alone or to temperature alone.

Any relevant mention of benefits of less mining (of copper ore)

Allow avoids depletion of (copper ore) resources

Less release of CO2 (or CO) into the atmosphere

Not just greenhouse gases. Must mention CO2 or COMax 2

[17]

of 80

(a) pH on the y-axis, volume of alkali on the x-axis

If axes unlabelled use data to decide that pH is on y-axis.1

27

Uses sensible scales

Lose this mark if plotted paths do not cover half of the paper.

Lose this mark if the graph plot goes off the squared paper.1

Labels the axes

Allow mark for axes labelled ‘pH’ and ‘volume’.1

Plots all of the points correctly1

Line through the points is smooth and has the correct profile

Ignore 0–5 cm3 section of the graph.

Lose this mark if graph is kinked or not a single line.1

Line ignores the point at 12 cm3

Lose this mark if point clearly not treated as an anomaly.1

(b) (i) 24.4 cm3 ± 0.2

If no answer in (i) allow answer written on the graph.

Allow this answer only.

Do not penalise precision.1

(ii) 12.2 cm3 ± 0.1

If no answer in (ii), allow answer written on the graph.

Allow answer to (i) divided by 2.


(iii) 3.9 ± 0.2

If no answer in (iii), allow answer written on the graph.

Consequential marking from (ii)

Lose this mark if answer not given to 1 dp.1

(c) pKa = – log Ka or Ka = 10x, where x = – (answer to b(iii))1

of 80

1.26 × 10–4

3.7 to 4.1 gives Ka = 7.9 × 10–5 to 2.0 × 10–4

Consequential marking from b(i).

Correct answer without working scores 1 mark only.


(d) Methanoic acid

Consequential marking from (c).

pKa = 3.7 gives methanoic acid.

pKa = 4.1 gives ethanoic acid.

No lucky guesses – candidates must apply answer from (c).

Do not allow answers based on data given in (f).1

(e) Error in using pipette is 0.2% andError in using burette is 0.15 × 100 / (answer to b(i))

Using 24.4 for burette gives 0.6%


Allow if errors are given without working.

Lose mark if the burette error is not calculated on b(i).

If the error being calculated is not stated, allow if the calculationsare in the same order as in the question (pipette, burette).

1

(f) Difference is 1.6 × 10–4 – 1.26 × 10–4 = 0.34 × 10–4

Allow consequential answer from (c).


0.34 × 100 / 1.6 is a 21% error

Correct final answer without working scores 1 mark.

Using 1.9 × 10–4 gives 0.3 × 10–4 and 18.8%.1

(g) Calibrate meter or thermostat the mixture or maintain constant temperature

Do not allow ‘repeat experiment’.1

(h) Mixture is a buffer1

[16]

(a) (i) Propanone evaporates (or similar)128

Removes water (from the precipitate)

Accept ‘removes impurities / excess reagents’.

Accept ‘salt insoluble in propanone’.1

of 80

(ii) Add NaOH / NH3 / Na2CO3

1

No green ppt

Accept ‘no visible change’.

Must have correct reagent to score this mark.1

(iii) Some salt dissolves (in propanone) or some lost in filtration or some Fe2+ getsoxidised (to Fe3+ in air)

Do not accept ‘reaction reversible’ or ‘incomplete reaction’ orsimilar.

1

(iv) Moles Fe2+ = 2.50 × 10−2

Accept 2.5 × 10−2

1

Mr of salt = 179.8

Allow 180

Allow if 179.8 or 180 appears in a calculation.1

Mass of salt = 179.8 × 2.5 × 10−2 × 0.95 = 4.27 (g)

Correct answer with no working scores this mark only.

Allow range 4.2 to 4.3 (g)1

(v) 1.67 mol or correct ratio of 5FeC2O4 : 3MnO4−

1

(b) Ca2+ + C2O42− → CaC2O4

Accept multiples.1

(c) (Insoluble) calcium ethanedioate coats surface

Allow ‘calcium ethanedioate is insoluble’.

Do not allow answers based on ethanedioic acid being a weak acid.

Do not accept ‘acid used up’ or ‘reaction very fast’.1

(d) Small amount of tea used or concentration of the acid in tea is low

Accept ‘high temperature decomposes the acid’.

Accept ‘calcium ions in milk form a precipitate with the acid’.

Do not accept ‘do not drink tea often’ or similar.1

(e) Mass of acid = 180.0 and mass of reagents = 450.0

Accept 180 and 450.1

of 80

(180 / 450 × 100 =) 40.0%


Correct answer without working scores this mark only.1

[14]

(a) Log (1 / time) on the y-axis + log (vol) on x-axis

If axes unlabelled use data to decide that log (1 / time) is on the

y-axis1

29

Sensible scales

Lose this mark if the plotted points do not cover at least half of thepaper

Lose this mark if the graph plot goes off the squared paper

Lose this mark if plots a non-linear / broken scale

Lose this mark if uses an ascending y-axis of negative numbers1

Plots points correctly ± one square1

Line through the points is smooth

Lose this mark if the candidate’s line is doubled1

Line through the points is best fit – ignores last point

Must recognise that point at 25 cm3 is an anomaly

If wrong graph, mark consequentially on anomaly if correctlyplotted.

A kinked graph loses smooth and best fit marks1

(b) Uses appropriate x and y readings

Allow taken from table or taken or drawn on graph

Must show triangle on graph or such as 1

Correctly calculates gradient 0.95 ± 0.02

Ignore positive or negative sign

Correct answer only with no working scores this mark1

Answer given to 2 decimal places1

(c) First order or order is 1

Allow consequential answer from candidate’s results1

of 80

(d) Thermostat the mixture / constant temperature / use a water bathor Colorimeter / uv-visible spectrometer / light sensor to monitor colour change

1

Reaction / rate affected by temperature changeor Eliminates human error in timing / more accurate time of colour change

1[11]

(a) Fractional distillation (under reduced pressure)130

(b) BaSO4 insoluble / remove by filtration

Do not allow answers which refer to reaction rate1

(c) Both contain OH group

Allow OH stretch in ir spectrum of each compound

Do not allow ‘same bonds’1

[3]

Figure 2131

Further oxidation will occur / ethanoic acid formed

Do not accept ‘poor yield’ without qualification

Can gain this mark if logic correct but has chosen wrong Figure1

[2]

(Calibrate) meter with solution(s) of known pH/buffer(s)

Do not accept ‘repeat reading’1

32

Adjust meter/plot calibration curve1

[2]

Sample in capillary / melting point tube

Accept alternative as long as small container used1

33

Heat in melting point apparatus / heat gently / slowly near melting point1

[2]

of 80

(a) percentage of oxygen is 58.331

correct calculation of ratios (C 3.125, H 4.17, O 3.645)1

clearly relates ratios to formula egsimplifies ratios (C 1, H 1.29, O 1.17) or for H then 3.125 × 8 / 6 = 4.17% etc

1

Notes* correct percentage of oxygen can be stated or shown clearly in a calculation* to score final mark must clearly show how ratios relate to C6H8O7

* allow full credit to candidate who correctly finds percentage of oxygen calculates Mr

shows percentage of H is 8 divided by Mr

34

(b) carbon dioxide / CO2

1

(c) (i) suitable reaction vesseleg sealed flask or test-tube with side arm oreg tube in bung

1

suitable collection methodeg gas syringe / over water in measuringeg cylinder

1

Notes* collection vessel must allow measurement of gas* if apparatus would leak lose second mark* ignore heating* can draw tubing as single line* accept 2D or 3D diagrams* do not need labels, and ignore mis-labelling

of 80

(ii) (1) mass on x-axis1

Notes * If axes unlabelled use data to decide that mass

is on the x-axis

sensible scales1

Notes * lose this mark if the plotted points do not cover at least half of the paper * lose this mark if the graph plot goes off the squared paper

plots points correctly ± one square1

(2) draws appropriate straight line of best fit, omitting point at 1.17g / 86 cm3

Notes * lose this mark if the line deviates towards the point at 1.17g / 86 cm3

* candidates does not have to extrapolate the line to the origin to score this mark * when checking for best fit, candidate’s line must go through the origin ± one square. Extend candidate’s line if necessary

1

(3) 129 ± 1 cm3

Notes * accept this answer only

1

(d) CO2 / gas formed distends stomach / produces wind / increases pressure in stomach1

(e) molecular formula has to be a simple multiple of the empirical formula1

so approximate Mr value will distinguish between the options or equivalent wording1

(f) gas escapes before bung inserted any 2 × 1 for

syringe sticks

carbon dioxide soluble in water

Notes* do not accept ‘operator error’ / ‘inaccurate equipment’ / ‘equipment leaks’

2

of 80

(g) volume depends on pressure and temperature

Notes* do not accept ‘to get a more accurate result’ or equivalent wording withoutqualification

1

(h) Tablets could vary between samples or equivalent wording

Notes* do not accept ‘to get a more accurate / reliable result’ or ‘to make a fair test’ withoutqualification

1

(i) (i) NaHCO3 least soluble1

(ii) exhaust gases passed into mixture of NaCl and NH3

1

(j) 2NaHCO3 → Na2CO3 + CO2 + H2O

Notes* accept multiples

1

(k) 106.0 divided by 217.1 × 100 = 48.8%

Notes* ignore precision of answer

1[22]

(a) sulfuric acid / H2SO4

135

(b) hydriodic acid / HI OR hydrobromic acid / HBr1

(c) add dilute ammonia solution

Notes* do not allow ‘concentrated ammonia’ or ‘ammonia ’

1

precipitate / ppt disappears / dissolves OR colourless solution forms1

(d) would react with the acid / no gas evolved in tests1

[5]

(a) Mass of mineral on x-axis;

If axes unlabelled use data to decide if mass of mineral is on the

x-axis.1

36

of 80

Sensible continuous scales;

Lose this mark if the plotted points do not cover at least 9 squaresby 7.Lose this mark if the graph plot goes off the squared paper.The graph does not have to start at the origin.

1

Plots points correctly ± one square;

Award this mark if the line is close to your line.1

Draws a best fit straight line

Award this mark if best fit line is consistent with candidate’s plottedpoints.Lose this mark if line is kinked or doubled.

1

(b) 1.48 or 1.49 or 1.50 or 1.5 (g);

Accept these answers onlyIgnore precision of answer.Allow range 1.48 – 1.5

1

(c) 0.0124 (mol);

Accept 0.012, 0.0125.Allow answer without working.

1

(d) (1.49 / 0.0124) = 119.4 – 125.0;

Must divide answer to part (b) by answer to part (c) to score firstmark.Allow consequential answer from part (b).Allow answer without working.Ignore precision of answer.

1

(e) Answer to part (e) close to 120.3;

Allow consequential answer from part (d).

Allow correct calculation of x1

(f) x must be a whole number;1

(g) Good / straight line so results good / reliable;

Allow consequential answers from candidate’s graphDo not allow ‘so results are accurate’.

1

Anomaly at 1.34 g;

Allow anomaly clearly indicated on the graph.1

of 80

(h) Ensure reaction / decomposition goes to completion;

Do not allow ‘to make fair test’ or ‘improve reliability’Accept to ‘remove all carbon dioxide and water’.

1

(i) (i) Percentage errors too high / errors in weighing too high;

Do not allow ‘to make fair test’ or ‘improve reliability’Do not allow ‘errors’ on its own.

1

(ii) Incomplete decomposition or words to that effect;

Do not allow ‘to make fair test’ or ‘improve reliability’Do not allow ‘takes too long’ or ‘wastes chemicals’Do not allow ‘not all of the water removed’.

1

(j) 39.05 / 18 = 2.170 and 60.95 / 84.3 = 0.723;

Allow Mr of MgCO3.H2O = 138.31

MgCO3.3H2O;

54 / 138.3 + 39.05%MgCO3.3H2O without working scores 1 mark.

1

(k) Atom economy for Reaction 1 is (40.3 / 84.3) x 100 = 47.8%

Maximum 1 mark if no working.Ignore precision of answers.

1

Atom economy for Reaction 2 is (40.3 / 58.3) x 100 = 69.1%1

(l) No gas produced in stomach / won’t cause wind;

Do not allow ‘gas produced’ on its own.1

[19]

(a) Temperature / pressure;

Do not allow ‘amount’ or concentration of reactants.1

37

(b) Determine gradient;

Do not allow volume / time.Accept ‘steepness’ or ‘slope’

1[2]

Add (hydrochloric) acid to the mixture;

Allow correct acid eg nitric acid.1

38

of 80

Filter to isolate strontium sulphate;

Do not allow ‘drain’ or decant’1

[2]

(a) Eliminate / reduce fire risk;

Allow ethanol flammable / burns / combusts.1

39

(b) Orange to green;

Need full colour change to score mark.1

[2]

Acidified potassium dichromate(VI)1

Turns green with propan-2-ol and propanal1

No reaction with hexene and 1-bromopropane1

Tollens with propan-2-ol and propanal1

only propanal gives silver mirror1

Bromine water1

Decolourised by hexane1

No reaction with 1-bromopropane1

Warm NaOH followed by acidified AgNO3

1White ppt with 1-bromopropane

1[10]

40

(a) Species [Co(H2O)6]2+

1

Precipitate Co(H2O)4(OH)2

1

41

(b) [Co(NH3)6]2+

1

(c) Reaction Oxidation1

Reactant Oxygen in the air1

of 80

(d) R Iodine1

Explanation [Co(H2O)6]3+ oxidises I– to I21

[7]

(a) Increase1

Van der Waal’s forces between molecules1

Increase with size (or Mr or surface area etc)1

More energy needed to break (overcome) these forces

(Note max 2 from last three marks if no mention of molecules or‘molecular’)

1

42

(b) (i) Brown solution (or yellow or orange)1

Cl2 + 2Br → 2C1– + Br2

1

(ii) cream precipitate1

Br– + Ag+ → AgBr1

Precipitate dissolves1

(iii) orange (brown) fumes (gas), White fumes (or misty fumes),choking gas (any 2)

2

(c) 2H+ + H2SO4 + 2Br– → SO2 + Br2 + 2H2O (SO2 and Br2 (1),equation (1))

2[13]

of 80

(1) alcohols can be oxidised by an acidified solution of potassium dichromate(Vl). Aldehydes can be...

Documents

Transcript of (1) alcohols can be oxidised by an acidified solution of potassium dichromate(Vl). Aldehydes can be...