Chemistry 9701 · AS & A Level · Reaction kinetics

Reaction kinetics — practice question

The equation $\text{2NO(g)} + \text{O}_2\text{(g)} \rightarrow \text{2NO}_2\text{(g)}$ shows the oxidation of nitrogen(II) oxide. Initial rates were then measured using several different starting concentrations of the two reactants. The outcomes are listed below.
(a(i))[2]

Use the figures in the table to work out the order for each reactant. Show how you arrive at your answer.

(a(ii))[1]

Calculate the initial rate in experiment $4$. Give your answer to two significant figures.

(a(iii))[1]

Write the rate equation that applies to this reaction.

(a(iv))[2]

Use the results of experiment $1$ to calculate the rate constant, $k$, for this reaction. Include the units of $k$.

(b(i))[3]

On the axes below, draw two Boltzmann distribution curves for two different temperatures, $T_1$ and $T_2$ ($T_2 > T_1$), and label both the curves and the axes.

(b(ii))[2]

State and explain, using your diagram, how increasing temperature affects the rate of reaction.

(c)[2]

Nitrosyl fluoride, NOF, can be produced by the reaction $\text{2NO(g)} + \text{F}_2\text{(g)} \rightleftharpoons \text{2NOF(g)}$. The rate is first order in NO and $\text{F}_2$. The reaction mechanism consists of two steps. Suggest equations for both steps, and state which one is the slower, rate determining step.

Worked solution & mark scheme

This 13-mark question has a full step-by-step worked solution and mark scheme. One marking point: [NO] is 2$^{nd}$ order; doubling the concentration makes the rate rise by a factor of 4

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