Chemistry 9701 · AS & A Level · Reaction kinetics

Reaction kinetics — practice question

Nitrosyl chloride, NOCl, may be produced when nitrogen monoxide reacts with chlorine, as shown: $2\text{NO} + \text{Cl}_2 \rightarrow 2\text{NOCl}$. The initial rate of this reaction is examined using a range of starting concentrations of NO and $\text{Cl}_2$. The findings are given in Table 5.1.
(a(i))[3]

Use the information in Table 5.1 to determine the rate equation for this reaction. Give an explanation for your deduction.

(a(ii))[2]

Use your rate equation from (a)(i) together with the data from experiment 1 to work out the rate constant, $k$, for this reaction. Give the units of $k$ too.

(b)[2]

$\text{NO}_2\text{Cl}$ is another compound that contains nitrogen, oxygen and chlorine. In sunlight, $\text{NO}_2\text{Cl}$ can undergo homolytic fission to produce chlorine radicals that catalyse the conversion of ozone, $\text{O}_3$, into oxygen. Complete the mechanism for this process. Initiation (homolytic fission): $\text{NO}_2\text{Cl} \rightarrow \dots + \dots$ Propagation step 1: $\dots + \text{O}_3 \rightarrow \dots + \dots$ Propagation step 2: $\dots + \dots \rightarrow \dots + \dots$

(c)[2]

Ozone reacts with nitrogen dioxide, as shown: $\text{O}_3 + 2\text{NO}_2 \rightarrow \text{N}_2\text{O}_5 + \text{O}_2$. The reaction is first order with respect to $\text{O}_3$ and first order with respect to $\text{NO}_2$. Suggest equations for a two-step mechanism for this reaction. Step 1: Step 2:

Worked solution & mark scheme

This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: $NO$ is second order

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