Chemistry 9701 · AS & A Level · Nitrogen compounds

Nitrogen compounds — practice question

Each year, more than one million tonnes of hydrogen cyanide, HCN, are made by the Andrussow process. The overall equation for the reaction is shown. $\text{CH}_4(g) + \text{NH}_3(g) + \tfrac{3}{2}\text{O}_2(g) \rightleftharpoons \text{HCN}(g) + 3\text{H}_2\text{O}(g)$
(a(i))[3]

Draw a dot-and-cross diagram to show the bonding in ammonia, $\text{NH}_3$, and state the shape of the molecule.

(a(ii))[2]

The bond between carbon and nitrogen is made up of one sigma ($\sigma$) bond and two pi ($\pi$) bonds. Sketch the shape of the sigma bond and one pi bond in the space below. Show the positions of the atomic nuclei clearly in each diagram.

(b(i))[1]

Explain what is meant by dynamic equilibrium.

(b(ii))[2]

State and explain how the amounts of the chemicals present in the equilibrium mixture will change when the pressure is increased.

(c)[3]

Sketch a Boltzmann distribution on the axes given below and use your diagram to explain how the platinum catalyst increases the rate of the reaction.

(d(i))[1]

The reaction of hydrogen cyanide with propanone is an important first step in many organic syntheses. Give the full name of the mechanism for this reaction.

(d(ii))[5]

Complete the diagram to show the mechanism for the reaction between hydrogen cyanide and propanone. Draw the intermediate structure and the reaction product. Include every relevant charge, partial charge, curly arrow and lone pair.

Worked solution & mark scheme

This 17-mark question has a full step-by-step worked solution and mark scheme. One marking point: Three bonding pairs are shown

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