Chemistry 9701 · AS & A Level · Reaction kinetics

Reaction kinetics — practice question

The compound nitrosyl bromide, NOBr, may be produced by the reaction shown. $2\text{NO} + \text{Br}_2 \rightleftharpoons 2\text{NOBr}$
(a)[2]

Using oxidation numbers, explain why this reaction counts as a redox reaction.

(b)[2]

Nitrosyl bromide has a trivalent nitrogen atom. Draw the ‘dot-and-cross’ diagram for NOBr. Show outer electrons only.

(c(i))[1]

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

(c(ii))[2]

Use the data in the table to deduce the values of $a$ and $b$ in the rate equation. Show your reasoning.

(c(iii))[1]

Use the data in the table to calculate the initial rate for experiment 4.

(c(iv))[2]

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

(c(v))[1]

By considering the rate equation, explain why the rate decreases with decreasing temperature.

(d)[1]

The reaction between X and Y was investigated. $2\text{X} + \text{Y} \rightarrow \text{Z}$ The following sequence of steps is a suggested mechanism for the reaction. step 1: $2\text{X} \rightarrow \text{V}$ step 2: $\text{V} + \text{Y} \rightarrow \text{Z}$ The general form of the rate equation for this reaction is shown below. $\text{rate} = k[\text{X}]^m[\text{Y}]^n$ Step 1 is the slower step in the mechanism. Deduce the values of $m$ and $n$ in the rate equation.

Worked solution & mark scheme

This 12-mark question has a full step-by-step worked solution and mark scheme. One marking point: Nitrogen oxidation state changes from $+2$ to $+3$ (oxidised)

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