Chemistry 9701 · AS & A Level · Nitrogen and sulfur

Nitrogen and sulfur — practice question

The diagram, at a specified temperature $T$, presents a Boltzmann distribution for the kinetic energy of the molecules in a mixture of two gases that react with each other. The activation energy for the reaction, $E_a$, is shown.
(a(i))

On the graph, sketch a second distribution curve, labelled $T'$, for the same gas mixture at the higher temperature, $T'$.

(a(ii))

On the energy graph opposite, mark the activation energy of the reaction at the higher temperature, $T'$, clearly as $H$.

(b)[2]

Explain what is meant by the term activation energy.

(c(i))

State the catalyst used and give the operating temperature and pressure of the Haber process.

(c(ii))

On the energy axis of the graph opposite, mark the position, clearly labelled C, of the activation energy for the reaction when a catalyst is used.

(c(iii))[3]

Use your answer to (ii) to explain how using a catalyst makes reactions happen faster.

(d)[4]

Two reactions that use aqueous NaOH are shown below: $\text{CH}_3\text{CHBrCH}_3 + \text{NaOH} \rightarrow \text{CH}_3\text{CH(OH)CH}_3 + \text{NaBr}$ (reaction 1) $\text{HCl} + \text{NaOH} \rightarrow \text{NaCl} + \text{H}_2\text{O}$ (reaction 2) For reaction 1 to happen, the reactants must be heated together for some time. By contrast, reaction 2 is almost instantaneous at room temperature. Suggest brief explanations for why the rates of these two reactions are very different.

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