Chemistry 9701 · AS & A Level · Reaction kinetics

Reaction kinetics — practice question

Chlorine dioxide, $\text{ClO}_2$, is produced by the reaction shown here: $\text{NaClO}_2 + \frac{1}{2}\text{Cl}_2 \rightarrow \text{ClO}_2 + \text{NaCl}$.
(a)[2]

Use oxidation numbers to show why this is a redox reaction.

(b)[2]

In the molecule of $\text{ClO}_2$, chlorine is the central atom. Draw the ‘dot-and-cross’ diagram for $\text{ClO}_2$. Show outer electrons only.

(c)

The reaction of $\text{ClO}_2$ with $\text{F}_2$ is shown: $2\text{ClO}_2 + \text{F}_2 \rightarrow 2\text{ClO}_2\text{F}$. The rate of reaction was measured at different concentrations of the two reactants and the results below were obtained. The rate equation is $\text{rate} = k[\text{ClO}_2][\text{F}_2]$.

(c(i))[1]

What does the term order of reaction with respect to a particular reagent mean?

(c(ii))[2]

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

(c(iii))[2]

Use the data in the table to calculate the initial rate in experiment 2, and $[\text{ClO}_2]$ in experiment 3.

(d(i))[1]

What is meant by the term rate-determining step?

(d(ii))[2]

The equation for the reaction between $\text{ClO}_2$ and $\text{F}_2$ is shown: $2\text{ClO}_2 + \text{F}_2 \rightarrow 2\text{ClO}_2\text{F}$ with $\text{rate} = k[\text{ClO}_2][\text{F}_2]$. The mechanism for this reaction has two steps. Suggest equations for the two steps of this mechanism, stating which of the two steps is the rate-determining step.

(e)[1]

Using the rate equation, explain why the rate increases as temperature rises.

Worked solution & mark scheme

This 13-mark question has a full step-by-step worked solution and mark scheme. One marking point: Oxidation number of Cl rises from $+3$ to $+4$ (oxidised).

  • Full mark scheme, point by point
  • Step-by-step worked solution
  • Write your answer & get it marked instantly by AI