C7 Name:- Target grade:- CAG:- Question overview

Question Topic Mark % Grade Date

C7a Green Chemistry /

C7b Catalysis /

C7c i Reactions of alcohols /6

C7c ii Reactions of alcohols /3

C7d Carboxylic acids /

C7ei Esters /5

C7eii Esters

C7f Fats /

C7gi Energy changes /8

C7gii Energy changes

C7hi Dynamic equilibrium /6

C7hii Dynamic equilibrium /2

C7i Chromatography /6

C7ii Chromatography /4

C7iii Chromatography

C7ji Titrations /7

C7jii Titration

C7jiii Titration

C7ki How science works /3

C7kii How science works /4

C7kiii How science works

7j Calculations /4

Colour code each subtopic using pencils, on target = orange, above = green, below = red

Green Chemistry

C7a Specimen5a

Epoxyethane is an intermediate in the production of car anti-freeze. It is also used to sterilise medical supplies.

Epoxyethane is poisonous, carcinogenic and highly flammable. The raw material used to make epoxyethane is ethene. This is obtained by the cracking of hydrocarbons from petroleum. Two different methods have been used to make epoxyethane. In the original method, epoxyethane was manufactured in a two stage process.

1 Ethene was passed into an aqueous solution of chlorine.

2 The reaction mixture was treated with calcium hydroxide.

The modern method involves only one step. Ethene and oxygen are passed over a silver catalyst at 250 – 350 oC.

(a) The sustainability of the two processes can be compared.

(i) Which two statements, when taken together, explain why the two methods are equally unsustainable?

Put ticks () next to the two correct answers.

Oxygen can be obtained from the air.

Ethene is obtained from crude oil.

Deforestation is reducing the amount of oxygen in the air.

Chlorine is obtained by electrolysis of brine.

Our supply of crude oil is finite.

The sea contains a very large reserve of sodium chloride. [2]

(ii) Which two statements explain why the original method is less sustainable in terms of by-products? Put ticks () next to the two correct answers.

Chlorine is a poisonous gas.

Hydrochloric acid is corrosive and its disposal can cause environmental problems.

There is little use for calcium chloride.

The original method produces water as a by-product.

Calcium hydroxide is an alkaline solid.

The new process has no by-products.

Catalysis

C7b Specimen 5b

b) A catalyst speeds up the reaction. Which two statements explain how a catalyst carries out this function?

Put ticks () next to the two correct answers.

The catalyst does not get used up during the reaction.

The catalyst has to be replaced frequently.

The catalyst lowers the activation energy for the reaction.

The catalyst provides an alternative route for the reaction.

The catalyst makes the reaction exothermic.

The catalyst raises the temperature of the reaction mixture.

Alcohols

C7ci 13Jun 6a

Ethanol can be made by the reaction of ethene with steam or by fermentation of sugar.

Method 1 – reaction of ethene with steam:

Ethene is obtained from crude oil. The ethene is reacted with steam at about 300 °C and 60 atmospheres pressure.

Method 2 – fermentation:

The sugar is obtained from crops such as sugar beet or sugar cane.

The sugar is fermented with yeast at a temperature of about 30 °C.

(a) The sustainability of chemical processes depends on a number of factors.

One of these factors is the renewability of raw materials.

Consider this, and other factors, to compare the sustainability of making ethanol by these two methods.

The quality of written communication will be assessed in your answer.

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C7c ii 13Jun6b

How do the reactions of ethanol, ethane and water with sodium compare?

Put ticks (✓) in the correct boxes to show what happens in each reaction

Carboxylic acids

C7d Specimen 1

Methanoic acid, HCOOH, is a carboxylic acid that is present in bee stings.

(a) What is the formula of the functional group that is responsible for the characteristic properties of carboxylic acids? .......................................................................................................................................... [1]

(b) Methanoic acid is used to remove the limescale in kettles. Limescale is made of calcium carbonate, which is insoluble in water. Carboxylic acids react with carbonates in a similar way to other acids such as hydrochloric acid.

Complete and balance this symbol equation for the reaction between calcium carbonate and methanoic acid

[2]

(ii) Calcium carbonate is insoluble so it stays inside the kettle. When calcium carbonate in limescale reacts with methanoic acid, calcium methanoate forms. The reaction with methanoic acid removes the calcium carbonate in limescale. Suggest a property of calcium methanoate that can explain why this happens.

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(iii) Methanoic acid is a weak acid and hydrochloric acid is a strong acid. Describe a reaction, other than with carbonates, that shows that methanoic acid is an acid. Compare this with a similar reaction of hydrochloric acid to demonstrate why one is a weak acid and the other a strong acid. Include relevant balanced equations in your answer. The quality of written communication will be assessed in your answer to this question.

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(c) Butanoic acid, C4H8O2, is responsible for the unpleasant taste in rancid butter. Draw a diagram to show the structural formula for butanoic acid. [1]

Esters

C7ei 13Jun1

Esters are made by reacting an alcohol with a carboxylic acid. A few drops of concentrated sulfuric acid are added to the mixture.

alcohol + carboxylic acid ester + water

(a) What is the job of the concentrated sulfuric acid?

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(b) The reaction mixture has to be heated for some time. The reactants are volatile and would escape from an open flask as vapour.

(i) What piece of apparatus is fitted to the flask to prevent this loss of vapour?

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(ii) What is the name of the technique used to prevent this loss of vapour?

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(c) Propyl pentanoate, C4H9COOC3H7, is an ester that tastes of pineapples.

It is made by reacting propanol, C3H7OH with pentanoic acid C4H9COOH.

(i) Write a symbol equation for the reaction that makes propyl pentanoate.

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(ii) Suggest a use for propyl pentanoate.

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[Total: 5]

Fats

C7g Specimen2a

Sunflower oil is an example of a vegetable oil. The oil comes from the seeds of the sunflower plant. The chemicals in the oil are esters.

(a) When an ester is hydrolysed it forms an alcohol and a carboxylic acid. This reaction is the reverse of the reaction that makes the ester. Oils and fats are esters. Write the name of the alcohol and the type of carboxylic acid to complete this word equation for the hydrolysis of an oil.

oil + water ⇋ ............................................ + ............................................... [1]

Energy changes

C7gi 13Jun4

The table shows the energy involved in the breaking of some bonds

Ethanol burns to make carbon dioxide and water

(a) The energy needed to break all of the bonds in the oxygen, 3O2, is 1494 kJ.

Work out the energy needed to break all of the bonds in ethanol, C2H5OH.

energy = .............................................. kJ/mol [2]

(b) The energy given out when new bonds in 2CO2 are made is 3196 kJ.

Work out the energy given out when new bonds in the water, 3H2O, are made.

energy = .............................................. kJ/mol [2]

(c) Use the information given, and your answers from (a) and (b), to complete the table.

(d) The table shows information about some bonds

What conclusions can you make from this data?

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C7gii Specimen6

Natural gas is used as a fuel. It contains the hydrocarbon methane.

(a) Methane burns in air according to this equation.

Energy changes are involved in the breaking and making of bonds when methane burns. Use ideas about the energy involved to explain why this reaction of methane with oxygen is exothermic.

The quality of written communication will be assessed in your answer to this question.

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Dynamic equilibrium

C7h 13Jun3a

Ammonia, NH3, is made from nitrogen and hydrogen by the Haber process.

(a) The graph shows how the yield of ammonia is related to both the temperature and the

pressure used.

(i) The Haber process uses:

• a catalyst

• a temperature of 450 °C

• 250 atmospheres pressure.

These conditions do not give the highest percentage yield of ammonia.

Explain why these conditions are a compromise to make the process economically

viable.

The quality of written communication will be assessed in your answer.

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(ii) The reaction between nitrogen and hydrogen to form ammonia is reversible.

The reaction mixture can reach a dynamic equilibrium.

Which of these statements describes what is happening at equilibrium?

Put ticks (✓) in the boxes next to the two correct statements.

The reaction between nitrogen and hydrogen has stopped.

The forward and reverse reactions happen at the same rate.

All of the nitrogen and hydrogen react to make ammonia.

The concentration of ammonia is increasing.

The concentrations of nitrogen, hydrogen and ammonia are constant.

Chromatography

C7i 13Jun2

Peter is testing the food colourings in soft drinks made by different companies.

He wants to find out if any of these drinks contains a banned dye chemical.

Peter uses paper chromatography to separate and identify the dye chemicals in the soft drinks.

Here is Peter’s chromatogram for one of the soft drinks

(a) Explain why the three spots travel different distances up the chromatogram.

The quality of written communication will be assessed in your answer.

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(b) Peter uses Rf values to identify the dye chemicals in a soft drink.

(i) Work out the Rf value of spot 3.

Rf value = .......................................................... [2]

(ii) Peter finds the Rf values for dye chemicals in several different soft drinks.

How can Peter check if any of the soft drinks contain a banned dye chemical?

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C7i ii Specimen3

3 A technician analyses a mixture of hydrocarbons using gas chromatography. She first calibrates the equipment using standard hydrocarbons. The retention times of these hydrocarbons are shown in the table.

(a) The technician then analyses the mixture of hydrocarbons. The recorder print out from this analysis is shown below

(i) How does the recorder print out show that butane has the highest concentration? .....................................................................................................................................................................

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(ii) Use data in the table to draw a conclusion relating the formula of each hydrocarbon to its retention time. .....................................................................................................................................................................

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(b) During gas chromatography, each component of a mixture is involved in a dynamic equilibrium. Explain how this separates the components in a mixture. The quality of written communication will be assessed in your answer to this question.

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Titrations

C7j 13Jun5a

Emma works for a company making indigestion tablets. Her job is to find the mass of magnesium hydroxide in tablets from each batch. Emma titrates the magnesium hydroxide in each tablet with hydrochloric acid.

(a)

(i) What steps should Emma take to ensure that her titration results are as accurate as possible? Put ticks (✓)next to the two correct statements.

Add the acid as quickly as possible.

Use a burette to measure the volume of acid.

Add acid 1 cm3 at a time.

Add acid drop by drop near the end point.

Measure the mass of the flask every 30 seconds.

Allow the product to crystallise

(ii) Emma uses an indicator in her titration.

Explain why she uses an indicator.

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(b) Emma analyses an indigestion tablet to find the mass of magnesium hydroxide.

(i) Work out the relative formula mass (RFM) of magnesium hydroxide, Mg(OH)2.

Show your working.

(Relative atomic masses: H = 1; Mg = 24; O = 16)

RFM of magnesium hydroxide = .......................................................... [1]

(ii) Emma uses hydrochloric acid with 73.0 g of hydrogen chloride in each 1.0 dm3 of the acid solution. It takes 15.1 cm3 of this hydrochloric acid to neutralise the tablet.

Work out the mass of hydrogen chloride in 15.1 cm3 of the hydrochloric acid.

Give your answer to the nearest 0.1 g.

Show your working.

mass of hydrogen chloride = ...................................................... g [2]

(iii) Work out the mass of magnesium hydroxide in the tablet.

Use your answers to (i) and (ii) and this equation to help you.

mass of magnesium hydroxide in the tablet = ...................................................... g [2]

C7jii Specimen4ai,ii,iii

4 A company makes indigestion tablets that contain the active ingredient magnesium hydroxide. This neutralises excess stomach acid to relieve the symptoms of acid indigestion.

The tablets also contain starch.

A chemist analyses samples from each batch of indigestion tablets that the company makes. He uses quantitative analysis to find the mass of active ingredient in each tablet.

He tests 5 tablets from one batch. He makes a suspension of each of the five tablets and titrates these with a solution containing hydrochloric acid.

The concentration of this acid is 40.0 g/dm3 .

His results are shown in the table.

(a) Use the average of his results to work out the average mass of magnesium hydroxide in each tablet in the following way.

(i) Work out the relative formula mass (RFM) of magnesium hydroxide, Mg(OH)2.

Relative atomic masses are given in the Periodic Table on the back page. Show your working.

relative formula mass (RFM) = ......................... [1]

(ii) Work out the mass of hydrochloric acid in 23.5 cm3 of the hydrochloric acid solution used in the titrations.

mass = ................... g [1]

(iii) Use the neutralisation equation below to work out the mass of magnesium hydroxide that reacts with this mass of hydrochloric acid. This is the average mass of magnesium hydroxide in each tablet. The relative formula mass of hydrochloric acid, HCl, is 36.5.

average mass of magnesium hydroxide in each tablet = ............................................ g [2]

C7jiii Specimen7

Gemma works for a company making vinegar. Each day she measures the amount of ethanoic acid in 25.0 cm3 samples of the vinegar made. She carries out a titration using a standard solution of sodium hydroxide and an indicator. (a) Gemma makes her standard solution of sodium hydroxide to use for her titration. The statements describe how she makes up this solution, but they are in the wrong order

(i) Write the letters of these statements in the boxes to show the correct order. The first and last have been done for you.

[3](ii) Calculate the concentration of her sodium hydroxide solution in g/dm3

concentration of sodium hydroxide solution = ...................................................... g/dm3 [1]

How science works

C7ki 13Jun3c

(c) Look at the bar chart

The main use of ammonia is to make fertilisers.

Large scale use of fertilisers made from ammonia causes environmental problems.

Write about these problems, and explain why they have got worse over the last 60 years.

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C7kii 13Jun5c

Emma analyses six indigestion tablets from each of a series of batches.

The table shows Emma’s results for four batches of tablets

The label on each pack of indigestion tablets says that each tablet contains 1.0 g of magnesium hydroxide.

The standard set by the company is that each tablet must be within 0.1 g of this figure.

For each batch decide whether it meets the standard and explain your answers.

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C7kiii Specimen4aiv,4b

A company makes batches of 100 000 tablets. The chemist samples and tests some tablets from each batch to obtain data about the mass of magnesium hydroxide in the tablets. Look at his results.

Suggest what changes the chemist should make to the testing procedure. .............................................................................................................................................

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(c) Use the table of titration results to assess the degree of uncertainty in your calculated value of the mass of magnesium hydroxide in each tablet. Explain your answer. .....................................................................................................................................................

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Calculations

C7l 13Jun3b

Work out the relative formula mass (RFM) of ammonia, NH3.

RFM of ammonia = .......................................................... [1]

(ii) What is the mass of ammonia that would be made if 1.0 tonne of nitrogen reacted

completely with hydrogen?

Show your working.

mass of ammonia = ............................................... tonne [2]

(iii) A factory converts 95 % of the nitrogen into ammonia.

What mass of ammonia does this factory make from each tonne of nitrogen?

mass of ammonia = ............................................... tonne

(iii) A factory converts 95 % of the nitrogen into ammonia.

What mass of ammonia does this factory make from each tonne of nitrogen?

mass of ammonia = ............................................... tonne [1]