Chemistry 9701 · AS & A Level · Nitrogen and sulfur

Nitrogen and sulfur — practice question

The Haber process used to make ammonia, $\text{NH}_3$, was first developed in the early 20th century and Carl Bosch later turned it into a large-scale industrial process in 1913. Its crucial stage is the reversible reaction between nitrogen and hydrogen in the presence of an iron catalyst. $\text{N}_2\text{(g)} + 3\text{H}_2\text{(g)} \rightleftharpoons 2\text{NH}_3\text{(g)}$ with $\Delta H = -92\ \text{kJ mol}^{-1}$.
(a)[1]

Hydrogen for this reaction may be prepared by reacting methane with steam, and carbon monoxide is also produced in the process. Write an equation for this reaction.

(b)[4]

Using the Boltzmann distribution shown, explain why a catalyst raises the rate of this reaction.

(c)[3]

Draw a three-dimensional diagram to show the shape of an ammonia molecule. Name the shape and state the bond angle.

(d(i))[4]

Using Le Chatelier’s Principle and reaction kinetics, state and explain one benefit and one drawback of using a higher temperature.

(d(ii))[1]

State the equilibrium constant expression, $K_p$, for making ammonia from nitrogen and hydrogen in the Haber process.

(d(iii))[5]

A vessel initially contains $2.00$ moles of nitrogen and $3.00$ moles of hydrogen and is allowed to reach equilibrium. When equilibrium is reached, the pressure is $2.00 \times 10^7\ \text{Pa}$ and the mixture has $1.60$ moles of ammonia. Calculate $K_p$. Include the units.

Worked solution & mark scheme

This 18-mark question has a full step-by-step worked solution and mark scheme. One marking point: Balanced equation: $CH_4 + H_2O \rightarrow CO + 3H_2$.

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