Essential Chemistry SPM Question Bank

Chapter 10: Rate of Reaction

Paper 1

1)

The above diagram is the energy profile diagram for an exothermic reaction. Among A, B, C and D , which represents the activation energy of the reaction?

2) Which of the following explains why the rate of hydrogen released decreases with time?

Zn + 2HCl ZnCl2 + H2

I Mass of zinc decreasesII Mass of zinc chloride increasesIII Concentration of acid decreasesIV Volume of acid decreasesA III only C I and III onlyB I and II only D I, III and IV only

3) Which of the following acids produces the highest initial rate of reaction if 6 g of calcium carbonate is put into it?A 50 cm3 of 0.5 mol dm-3 hydrochloric acid B 50 cm3 of 1 mol dm-3 sulphuric acid C 50 cm3 of 1 mol dm-3 hydrochloric acidD 100 cm3 of 5 mol dm-3 ethanoic acid

4) Graph P in the diagram below is obtained from the reaction between 5 g of zinc powder (in excess) and 50 cm3 of 2 mol dm-3 hydrochloric acid.

Progress of reaction

A

B

D

C50

Energy / kJ

100

170

Volume of gas / cm3

Time /s

P

Q

Which of the following are probably the reactants that produce graph Q?A 5 g of zinc pieces and 50 cm3 of 2 mol dm-3 hydrochloric acidB 6 g of zinc powder and 50 cm3 of 1 mol dm-3 hydrochloric acidC 6 g of zinc pieces and 100 cm3 of 1 mol dm-3 hydrochloric acidD 5 g of zinc pieces and 100 cm3 of 2 mol dm-3 hydrochloric acid

5) The diagram below is the energy profile diagram of a reaction.

Which of the following changes the activation energy from Ea to Eb?A Concentration C CatalystB Temperature D Total surface area

6) Graph I in the diagram below shows the graph of volume of gas against time for the reaction between 6 g of zinc pieces and 50 cm3 of 1 mol dm-3 sulphuric acid.

Which of the following must be done to produce Graph II?A Cool the sulphuric acidB Add 10 cm3 of 0.5 mol dm-3 sulphuric acidC Replace the zinc pieces with zinc powderD Add copper(II) sulphate solution

P + Q

R + S

Progress of reaction

Ea

50

Energy / kJ

100

170

Eb

Volume of gas / cm3

Time /s

II

I

7) Which of the following shows correctly the graph of concentration of solution against rate of reaction for the reaction between sodium thiosulphate solution and dilute hydrochloric acid? A C

B D

8) The diagram below shows the graph of volume of gas against time for the reaction between calcium carbonate and dilute hydrochloric acid.

What is the mass of calcium carbonate that reacts with the acid in this experiment? [Relative formula mass: CaCO3 = 100; Molar volume = 24 dm3 mol-1 at room condition]A 1 g C 20 g B 10 g D 24 g

9) The reaction between dilute nitric acid and zinc produces hydrogen. This reaction is completed within 60 seconds and the maximum volume of gas released is 120 cm3. Calculate the average rate of reaction.A 0.5 cm3 s-1 C 1.5 cm3 s-1

B 1.0 cm3 s-1 D 2.0 cm3 s-1

Concentration

Rate of reaction

Concentration

Rate of reaction

Concentration

Rate of reaction

Concentration

Rate of reaction

Volume of gas / cm3

Time /s

240

10) Which of the following is a characteristic of a catalyst?A Specific in its reactionB Influences the amount of product C The chemical property of catalyst changes at the end of the reactionD A lot of catalysts are needed to influence the rate of reaction

Paper 2

Structured question

Two experiments are conducted to study the effect of a catalyst on the rate of reaction between marble chips and hydrochloric acid.

Experiment I 10 g of zinc pieces (in excess) and 50 cm3 of 0.2 mol dm-3 hydrochloric acidExperiment II 10 g of zinc pieces (in excess), 50 cm3 of 0.2 mol dm-3 hydrochloric acid and

2 cm3 of copper(II) sulphate solution

(a) Write the chemical equation to show the reaction that occurs.(b) What is the role of copper(II) sulphate solution in this experiment?(c) Sketch the graph of volume of gas collected against time for both experiments on the same

axes.

(d) (i) In which experiment is the rate of reaction between zinc and hydrochloric acid higher? (ii) Explain your answer in (d)(i) based on the collision theory.

(e) Calculate the maximum mass of zinc that reacts in this experiment.[Relative atomic mass: Zn = 65]

(f) State three other factors besides the catalyst that affects the rate of reaction in this experiment.

Volume of gas

Time

Essay question(a) Porridge that is stored in a refrigerator will last longer than porridge that is placed on the

dining table. Explain this statement.[4

marks](b) Three experiments had been carried out to investigate the factors affecting the rate of

reaction. The table below shows the reaction condition for each of the experiments.

Experiment ReactantsI Excess zinc pieces and 25 cm3 of 0.1 mol dm-3 hydrochloric acid II Excess zinc pieces and 25 cm3 of 0.2 mol dm-3 hydrochloric acid III Excess zinc powder and 25 cm3 0.2 mol dm-3 hydrochloric acid

(i) Sketch the graph of volume of gas collected against the time for Experiments I, II and III, using the same axes. [3 marks]

(ii) The chemical equation below shows the reaction between zinc and hydrochloric acid.Zn + 2HCl ZnCl2 + H2

Given that the relative atomic mass of H = 1, Cl = 35.5, Zn = 65, and the molar volume of any gas is 24 dm3 mol-1 at room temperature and pressure, calculate the maximum volume of hydrogen produced in Experiment I. [4 marks]

(c) Calculate the average rate of reaction for Experiment I if the maximum volume of hydrogen

is collected in 120 seconds. [2 marks](d) Based on the graph drawn in (b)(i), compare the rate of reaction between Experiment II and

Experiment III. Explain the difference in the rate of reaction with reference to the collision theory. [4 marks]

(e) The rate of reaction in Experiments I, II and III can be increased by adding copper(II) sulphate solution. Explain the role of copper(II) sulphate solution based on the collision theory. [3 marks]

Paper 3

Based on the situation above, plan an experiment to investigate the effect of reactant size on the rate of reaction between a named metal and a named acid.Your plan must include the following items:

(i) Aim of experiment [State the aim of the experiment](ii) All the variables [State the hypothesis](iii) Lists of materials and apparatus [List the materials and apparatus](iv) Procedure [Choose the procedure](v) Tabulation of data [Tabulate the data]

A small piece of charcoal is easier to light as compared with a big piece of charcoal.

Answers

Paper 1

1 A2 C3 B4 D5 C6 A7 B8 A9 D10 A

Paper 2Structured question

(a) Zn + 2HCl ZnCl2 + H2

(b) To increase the rate of reaction(c)

(d) (i) Experiment II(ii) Copper(II) sulphate (catalyst) provides an alternative route that requires a lower activation energy. With a lower activation energy, more particles will have effective collisions. (e)

0.005 mol 0.01mol Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)

? g V =50 cm3

M = 0.2 mol dm-3

MV = number of moles 1000 0.2 x 50 = 0.01 mol 1000 Number of moles of HCl = 0.01 mol

1 mol of Zn reacts with 2 mol of HCl 0.01/2 = 0.005 mol of Zn reacts with 0.01 mol of HCl Number of moles of Zn = 0.005 mol Therefore, mass of Zn = 0.005 x 65 = 0.325 g

Volume of gas / cm3

Time /s

I

II

(f) Temperature of reaction, size of zinc and concentration of hydrochloric acid

Essay question(a)- Bacteria is active at room temperature- Bacteria carry out biochemical processes- Bacteria produce toxins- The rate of food decay is higher at room temperature

(b)(i)

(ii)

0.0025 mol 0.00125 molZn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)

V = 25 cm3

M = 0.1 mol dm-3

MV = number of moles 1000 0.1 x 25 = 0.0025 mol 1000 Number of moles of HCl = 0.0025 mol 2 mol of HCl produces 1 mol of H2 0.0025 mol of HCl produces 0.0025/2 = 0.00125 mol of H2 Number of moles of H2 = 0.00125 mol Therefore, volume of H2 = 0.00125 x 24000 = 30 cm3

(c) Average rate of reaction = 30 = 0.25 cm3 s-1

120(d) - The rate of reaction in Experiment III is higher - The total surface area of zinc in Experiment III is larger - The collision frequency between zinc particles and hydrogen ion increases - The effective collision frequency increases

(e) - Copper(II) sulphate solution acts as a catalyst - The catalyst lowers the activation energy - Effective collision frequency increase

Time / s

Volume of gas

I

II

III

Paper 3(i) To study the effect of the reactant size on the rate of reaction(ii) Variable that is manipulated: Size of the zinc Variable that responds: Rate of reaction Variable that is fixed: Volume and concentration of the hydrochloric acid / mass of the zinc(iii) Material: 1 mol dm-3 of hydrochloric acid, 2 g of zinc pieces, 2 g of zinc powder Apparatus: Measuring cylinder, conical flask, stopwatch(iv) - 25 cm3 of 1 mol dm-3 hydrochloric acid is measured and poured into the conical flask

- 2 g of zinc pieces is put into the hydrochloric acid- The stopwatch is started immediately- The mixture of substances is shaken slowly- The time taken for all the zinc pieces to dissolve is recorded- The experiment is repeated using zinc powder- The volume and concentration of hydrochloric acid and the mass of zinc used are

the same(v)

Size of zinc Time taken /sZinc piecesZinc powder