MYP 10 Chemistry 2013-14Quantitative Chemistry Worksheet

Name: _________________________________ ( ) Class: _________ Date: _______________________________________________________________________________________________1.1 Mole concentration and Avogadro’s constant1.1.1 Apply the mole concept to substances.1.1.2 Determine the number of particles and the number of substance(in moles).1.2 Formulas1.2.1 Define the terms relative atomic mass (Ar) and relative molecular mass (Mr).1.2.2 Calculate the mass of one mole of a species from its formula.1.2.3 Solve problems involving the relationship between the amount of substances in moles, mass and molar mass.1.2.4 Distinguish between the terms empirical formula and molecular formula.1.2.5 Determine the empirical formula from the percentage composition or from other experimental data.1.2.6 Determine the molecular formula when given both the empirical formula and experimental data.

Molar Mass

1 mole of hydrogen atoms has a mass of __________g1 mole of hydrogen molecules has a mass of ____________g

Relative atomic mass

Relative molecular mass

The molar mass (Relative Molecular Mass) of Na2CO3.10H2O is _____________________________.

No. of moles =

A mole is the amount of substance that contains the same number of particles (atoms, ions, molecules etc.) as there are carbon atoms in 12g of C-12.

Avogadro’s constant (L) = 6.02 x 1023

No. of moles =

1. Calculate the number of moles of substance in each of the following.(a) 5.72g of sodium carbonate crystals, Na2CO3.10H2O(b) 2.01 x 1023 molecules of carbon dioxide

2. What is the number of hydrogen atoms in 4.80 g of methane ?Step 1: calculate the no of moles of methaneStep 2: calculate the no of moles of hydrogen atomsStep 3: calculate the no of hydrogen atoms using Avogadro’s number [7.22 x 1023]

3(a) Calculate the number of hydrogen atoms in 0.0100 ml of ammonia,NH3.(b) Calculate the total number of hydrogen atoms in 3g of C2H5OH (Mr = 46)(c) Calculate the number of molecules in 1.00g of table sugar, C12H22O11. [1.76 x 1021]

4. The relative molecular mass of aluminum chloride is 267 and its composition by mass is 20.3% Al and 79.7% chlorine. Determine the empirical and molecular formulas of aluminium chloride.

[IBO,2003]

5. On analysis of an organic acid X, it was found to contain 58.8% by mass of carbon, 9.80% by mass of hydrogen and the remainder being oxygen. Determine the percentage by mass of oxygen and the empirical formula of X.

6. For ammonium carbonate, calculate the percentage by mass of (a) carbon (b) nitrogen

7. The combustion of hydrocarbon fuels is an environmental concern as it adds to the carbon dioxide levels in the atmosphere. Calculate the mass of carbon dioxide produced when 100g of propane is burned according to the equation. C3H8(g) + 5O2(g) 3CO2(g) + 4H2O(l)

1.3 Chemical equations1.3.1 Deduce chemical equations when all reactants and products are given.1.3.2 Identify the mole ratio of any two species in a chemical equation.1.3.3 Apply the state symbols (s), (l), (g) and (aq).

1.4 Mass and gaseous volume relationships in chemical reactions1.4.1 Calculate theoretical yields from chemical equations.1.4.2 Determine the limiting reactant and the reactant in excess when quantities of reacting substances are given.1.4.3 Solve problems involving theoretical, experimental and percentage yield.1.4.4 Apply Avogadro’s law to calculate reacting volumes of gases.1.4.5 Apply the concept of molar volume at standard temperature and pressure in calculations.1.4.6 Solve problems involving the relationship between temperature, pressure and volume for a fixed mass of an ideal gas.1.4.7 Solve problems using the ideal gas equation, PV = nRT.1.4.8 Analyse graphs relating to the ideal gas equation.

8(a) Write an equation for the formation of zinc iodide from zinc and iodine. (b) 100.0g of zinc is allowed to react with 100.0g of iodine producing zinc iodide.

Calculate the amount (in moles) of zinc and iodine, and hence determine which reactant is in excess.

(c) Calculate the mass of zinc iodide that will be produced.[HL paper 2, May 04]

[(b)Zn:1.530mol,I2:0.3940mol(c)125.8g]

9. 0.600 mol of aluminium hydroxide is mixed with 0.600 mol of sulfuric acid, and the following reaction occurs:

2Al(OH)3 (s) + 3H2SO4 (aq) Al2(SO4)3 (aq) + 6H2O(l)

(a) Determine the limiting reactant.(b) Calculate the mass of Al2(SO4)3 produced.(c) Determine the amount(in mol) and mass of the excess reactant that remains.

[(b)68.4g(c)0.200mol, 255.6g]

10. Aspirin, C9H8O4, is made by reacting ethanoic anhydride, C4H6O3 (Mr = 102.1), with 2-hydroxybenzoic acid (Mr = 138.1), according to the equation:

2C7H6O3 + C4H6O3 2C9H8O4 + H2O(a) If 15.0g of 2-hydroxybenzoic acid is reacted with 15.0 g ethanoic anhydride, determine the limiting

reagent in this reaction.(b) Calculate the maximum mass of aspirin that could be obtained in this reaction.(c) If the mass obtained in this experiment was 13.7g, calculate the percentage yield of aspirin.

[(b) 19.6g (c)69.9%]

Molar Volume of a Gas

Standard conditions of temperature and pressure (stp) are 273K (00C) and 100 kPa

No. of moles =

11. Calculate (a) the amount(no. of moles) of a gas occupied by 89.6 cm3 at stp(b) the volume of 0.75 mol SO3.

12. Calcium reacts with water to produce hydrogen gas. Calculate the volume of gas measured at stp, produced when 0.200g of calcium reacts completely with water.

13. Consider the following equation:

2As2S3 + 9O2 2As2O3 + 6SO2

What volume of SO2 is obtained (measured at stp) when 1.000kg of As2S3 is heated in oxygen? [273dm3]

14. Calcium and hydrochloric acid react according to the equation:

Ca(s) + 2HCl(aq) CaCl2(aq) + H2(g)

0.122g of calcium metal was added to 25.0cm3 of 1.23 mol dm-3 solution of hydrochloric acid and the hydrogen gas was collected at room temperature and pressure.

(i) Calculate whether the calcium or hydrochloric acid was in excess.(ii) Hence calculate the volume of hydrogen gas produced. [HCl, 73.2cm3]

The Gas Laws

15. At 273 K and 101 325 Pa, 12.64 grams of a gas occupy 4.00 dm3. Calculate the relative molecular mass of a gas.

[70.7]

16. Calculate the relative molecular mass of a gas which has a density of 2.615 gdm-3 at 298 K and 101 325 Pa.

[63.9]

17(a) Write an equation for the reaction between hydrochloric acid and calcium carbonate.(b) Determine the volume of 1.50 moldm-3 of hydrochloric acid that would react with exactly 1.25g

of calcium carbonate.(c) Calculate the volume of carbon dioxide, measured at 273K and 1.01 x 105 Pa, which would be

produced when 1.25g of calcium carbonate reacts with the hydrochloric acid. [IBO, 2003]

18(a) The percentage composition by mass of a hydrocarbon is C = 85.6% and H=14.4%.(i) Calculate the empirical formula of the hydrocarbon.

(b) A 1g sample of the hydrocarbon at a temperature of 273K and a pressure of 1.01 x 105 Pa(1.00 atm) has a volume of 0.399dm3. (i) Calculate the molar mass of the hydrocarbon. (ii) Deduce the molecular formula of the hydrocarbon. [IBO 2005]

19. A hydrocarbon contains 88.8% C, 0.201g of the hydrocarbon occupied a volume of 98.3cm3 at 320K and 1.00 x 105Pa.

(a) Determine the empirical formula of the hydrocarbon.(b) Determine the molecular formula of the hydrocarbon.

20. 40cm3 carbon monoxide reacts with 40cm3 oxygen in the equation

2CO(g) + O2(g) 2CO2(g) Assuming that all volumes are measured at the same temperature and pressure,

(a) what is the volume of oxygen reacts with 40cm3 of carbon monoxide?(b) identify the limiting reagent.(c) what is the volume of carbon dioxide produced?

21. Assume all volumes are measured at the same temperature and pressure.(a) What volume of nitrogen forms when 100cm3 of ammonia decomposes completely into its elements?

2NH3(g) N2(g) + 3H2(g)

(b) What volume of oxygen is needed to react with 40 cm3 of butane, C4H10 and what volume of carbon dioxide is produced?

2C4H10(g) + 13O2(g) 8CO2(g) + 10H2O(l)

1.5 Solutions1.5.1 Distinguish between the terms solute, solvent, solution and concentration (gdm-3 and moldm-3)1.5.2 Solve problems involving concentration, amount of solute and volume of solution.

Solute

Solvent

Solution

Concentration

No. of moles

22. A solution of sodium carbonate has a concentration of 9.6 gdm-3. What is its concentration in moldm-3?

23. Calculate the concentration of a 0.08 moldm-3 solution of HCl in gdm-3.

Standard Solution : A solution of known concentration

24. Calculate the number of moles present in (a) 27.8 cm3 of 0.0840 moldm-3 HCl(b) 540 cm3 of 0.0200 moldm-3 KmnO4

25. Calculate the mass of magnesium sulfate heptahydrated, MgSO4.7H2O required to prepare 0.100 dm3

of a 0.20 moldm-3 solution.

26. If 29.70 cm3 of sulfuric acid of concentration 0.200 moldm-3 is required for neutralisation of 25.00 cm3 of potassium hydroxide solution. Calculate the concentration of the potassium hydroxide solution.

2KOH(aq) + H2SO4(aq) K2SO4(aq) + 2H2O(l)

27. What volume (in cm3) of 0.100 mldm-3 barium chloride must be reacted with excess sodium sulfate to produce 0.100g of barium sulfate.

BaCl2(aq) + Na2SO4(aq) BaSO4(s) + 2NaCl(aq)

28. Calculate the volume of carbon dioxide produced when 1g of calcium carbonate reacts with 20.0 cm3 of 2 moldm-3 hydrochloric acid. Assume the volume of this gas is measured at stp.

29. If 0.100g of magnesium is reacted with 25.00 cm3 of 0.200 moldm-3 hydrochloric acid, calculate the volume of hydrogen produced at stp.

30. A solution contains 15 g/dm3 of sodium carbonate crystals., Na2CO3.nH2O. Given that 25.0 cm3 of this solution requires 26.2 cm3 of 0.1 M hydrochloric acid for neutralisation using methyl orange as an indicator , calculate the value of n.

Dilution

1. Calculate the volume to which 25.0 cm3 of 5.0 moldm-3 hydrochloric acid must be diluted to produce a concentration of 1.5 moldm-3.

Volumetric Chemistry

Acid-base titrations include Determining the ___________________ of solutions Determining the percentage ___________ or ________________ of an acid or base Deducing the equation for a neutralisation reaction Determining the amount of water of crystallisation in a hydrated salt.

1. 17.5 cm3 of 0.150 moldm-3 potassium hydroxide react with 20.0cm3 of phosphoric acid, H3PO4 of concentration 0.0656moldm-3. Deduce the equation for the reaction.

2. A solution of sodium hydroxide contains 1.80g of hydroxide ions per dm3. 20.0cm3 of the solution reacts with 25.00 cm3 of 0.0400 dm3 phosphoric acid (H3PO4).(a) How many moles of sodium hydroxide react with 1 mole of phosphoric acid?(b) What will be the chemical equation for the reaction? [2]

3. A 50.0 cm3 sample of concentrated sulphuric acid was diluted to 1.00dm3. A sample of the diluted sulphuric acid was analysed by titrating with aqueous sodium hydroxide. In the titration,25.00 cm3 of 1.00moldm-3 aqueous sodium hydroxide required 20.0cm3 of the diluted sulphuric acid for neutralisation. Determine the concentration of the original concentrated sulphuric acid solution.

4. 40 cm3 of a HCl solution was diluted with water and made up to a 250 cm3 solution. 25.0 cm3 of this diluted solution required 20.90 cm3 of a 0.01 moldm-3 NaOH solution for complete neutralisation. What is the concentration of the original HCl solution? [0.0523 moldm-3]

5. Distilled water is added to 24.00 cm3 sulphuric acid to give a total volume of 250 cm3. When 25.0 cm3 of this solution is titrated, it required 22.80 cm3 of 1.325g dm-3 of NaOH. Calculate the original concentration of sulphuric acid. [0.157 mol dm-3]

Back Titration

1. Magnesium oxide is not very soluble in water, and is difficult to titrate directly. Its purity can be determined by use of a 'back titration' method. 4.06 g of impure magnesium oxide was completely dissolved in 100 cm3 of hydrochloric acid, of concentration 2.0 mol dm-3 (in excess). The excess acid required 19.7 cm3 of sodium hydroxide (0.20 mol dm-3) for neutralisation. This second titration is called a 'back-titration', and is used to determine the unreacted acid.

(a) write equations for the two neutralisation reactions.(b) calculate the moles of hydrochloric acid added to the magnesium oxide.(c) calculate the moles of excess hydrochloric acid titrated.(d) calculate the moles of hydrochloric acid reacting with the magnesium oxide.(e) calculate the mass of magnesium oxide that reacted with the initial hydrochloric acid, hence the

% purity of the magnesium oxide.(f) what compounds could be present in the magnesium oxide that could lead to a false value of its

purity? Explain your answer.

2. A student was asked to determine the concentration of ammonia, a volatile substance, in a commercially available cloudy ammonia solution used for cleaning. First the student pipetted 25.00mL of the cloudy ammonia solution into a 250.0mL conical flask. 50.00mL of 0.100M HCl(aq) was immediately added to the conical flask which reacted with the ammonia in solution. The excess (unreacted) HCl was then titrated with 0.050M Na2CO3(aq). 21.50mL of Na2CO3(aq) was required. Calculate the concentration of the ammonia in the cloudy ammonia solution.

[0.114M]

4. 0.500g of impure ammonium chloride is warmed with an excess of sodium hydroxide solution. The ammonia liberated is absorbed in 25.0 cm3 of 0.200 moldm-3 sulfuric acid. The excess of sulfuric acid requires 5.64 cm3 of 0.200 moldm-3 sodium hydroxide solution for titration. Calculate the percentage of ammonium chloride in the original sample.