Chemistry 9701 · AS & A Level · Reaction kinetics

Reaction kinetics — practice question

In aqueous solution, 2-chloro-2-methylpropane, $(\text{CH}_3)_3\text{CCl}$, undergoes reaction with sodium hydroxide, $\text{NaOH}$. This reaction is a nucleophilic substitution. $(\text{CH}_3)_3\text{CCl}(aq) + \text{NaOH}(aq) \rightarrow (\text{CH}_3)_3\text{COH}(aq) + \text{NaCl}(aq)$
(a)[3]

Show the mechanism for this reaction. Include every required curly arrow, lone pair and relevant dipole.

(b)

The graph below presents the results from the experiment used to investigate the rate of this reaction with a large excess of sodium hydroxide.

(b(i))[1]

What does the term half-life of a reaction mean?

(b(ii))[1]

Calculate the half-life for this reaction. Show all your working and make sure any construction lines on the graph are shown clearly.

(b(iii))[1]

What effect would doubling the initial concentration of $[(\text{CH}_3)_3\text{CCl}]$ have on the half-life of this reaction?

(c(i))[2]

Use the graph in (b) to find the rate of reaction at $80\,\text{s}$. Show all your working.

(c(ii))[1]

The rate equation for this reaction is given as: $\text{rate} = k[(\text{CH}_3)_3\text{CCl}]$. Calculate the value of the rate constant, $k$, for this reaction and state its units.

(i)[1]

What does the term half-life of a reaction mean?

(ii)[1]

Calculate the half-life for this reaction. Show all your working and make sure any construction lines on the graph are shown clearly.

(iii)[1]

What effect would doubling the initial concentration of $[(\text{CH}_3)_3\text{CCl}]$ have on the half-life of this reaction?

Worked solution & mark scheme

This 12-mark question has a full step-by-step worked solution and mark scheme. One marking point: Dipole marked on the C-Cl bond

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