Cambridge International A Level · Chemistry (9701)

Reaction kinetics (AS): Practice Questions

5 multiple-choice questions marked as you go, and 5 written questions with worked solutions. All on Reaction kinetics (AS).

10 questions25 marksFree, no account

Question 1

1 mark

What is the correct definition of activation energy, \( E_a \)?

Question 2

1 mark

The decomposition of a reactant X follows first-order kinetics. If the initial concentration of X is \(0.80 \text{ mol dm}^{-3}\) and its half-life is 20 minutes, what will the concentration of X be after 60 minutes?

Question 3

1 mark

In the oxidation of iodide ions by peroxodisulfate ions, \( S_2O_8^{2-} + 2I^- \to 2SO_4^{2-} + I_2 \), the reaction is catalysed by \( Fe^{2+}(aq) \).
Which set of equations correctly represents the homogeneous catalysis mechanism?

Question 4

1 mark

In the reaction between methane and chlorine, the first step is the homolytic fission of the \(Cl-Cl\) bond by ultraviolet light to form chlorine radicals. Which term best describes the minimum energy required for this specific step to occur effectively?

Question 5

1 mark

The reaction between hydrogen and nitrogen(II) oxide follows the rate equation: \( \text{rate} = k[NO]^2[H_2] \).
The following mechanism is proposed:
Step 1: \( 2NO \rightleftharpoons N_2O_2 \) (fast equilibrium)
Step 2: \( N_2O_2 + H_2 \to N_2O + H_2O \) (slow)
Step 3: \( N_2O + H_2 \to N_2 + H_2O \) (fast)
Why is the reaction second-order with respect to NO?

Question 6

2 marks

Define the term activation energy, \(E_a\), for a chemical reaction.

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Question 7

4 marks

Using the Boltzmann distribution, explain qualitatively why a small increase in temperature leads to a significant increase in the rate constant, \( k \).

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Question 8

5 marks

Describe the specific role of adsorption and desorption in the catalytic removal of oxides of nitrogen using a platinum-based catalytic converter in car engines.

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Question 9

4 marks

(a) Define the term rate of reaction. [1]
(b) Use the collision theory to explain why increasing the temperature of a reaction mixture increases the rate of reaction. [3]<\/p>

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Question 10

5 marks

The reaction between reactant X and reactant Y was studied at \(298\text{ K}\). The following experimental data were obtained:

Experiment	Initial [X] / \(\text{mol dm}^{-3}\)	Initial [Y] / \(\text{mol dm}^{-3}\)	Initial rate / \(\text{mol dm}^{-3}\text{ s}^{-1}\)
1	0.150	0.100	\(1.20 \times 10^{-4}\)
2	0.300	0.100	\(4.80 \times 10^{-4}\)
3	0.300	0.200	\(9.60 \times 10^{-4}\)

(a) Deduce the order of reaction with respect to X and the order of reaction with respect to Y. Show your reasoning. [2]

(b) Construct the rate equation for this reaction. [1]

(c) Calculate the value of the rate constant, \(k\), for Experiment 1 and state its units. [2]

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