Chemistry 9701 · AS & A Level · Reaction kinetics

Reaction kinetics — practice question

Ethyl ethanoate undergoes slow hydrolysis by water in the acid-catalysed reaction below: $ \text{CH}_3\text{CO}_2\text{CH}_2\text{CH}_3 + \text{H}_2\text{O} \xrightarrow{\text{H}^+} \text{CH}_3\text{CO}_2\text{H} + \text{CH}_3\text{CH}_2\text{OH}$. The concentration of ethyl ethanoate was measured at set time intervals as the reaction proceeded. Two separate experiments were completed, each with a different $ ext{HCl}$ concentration. The graph below presents the outcomes for the experiment carried out with $[\text{HCl}] = 0.1\ \text{mol dm}^{-3}$.
(a(i))

For the run carried out with $[\text{HCl}] = 0.2\ \text{mol dm}^{-3}$, the results shown below were recorded. Plot these values on the axes above, then add a best-fit line.

(a(ii))

Use one of the graphs to demonstrate that the reaction is first order with respect to $\text{CH}_3\text{CO}_2\text{CH}_2\text{CH}_3$. Show every step of your working, and make sure any construction lines on the graphs are shown clearly.

(a(iii))

Use the graphs to work out the order of reaction with respect to HCl. Show every stage of your working, and make sure any construction lines on the graphs are shown clearly.

(a(iv))[7]

Write the rate equation for this reaction and work out the value of the rate constant.

(b(i))

Why can the order of reaction with respect to water not be found in this experiment?

(b(ii))[2]

Although $[\text{CH}_3\text{CO}_2\text{CH}_2\text{CH}_3]$ falls during each experiment, $[\text{HCl}]$ stays equal to its starting value. Why does this happen?

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