Chemistry 9701 · AS & A Level · Nitrogen and sulfur

Nitrogen and sulfur — practice question

In the Haber process, $\text{N}_2(g)$ combines with $\text{H}_2(g)$, as illustrated by reaction 1. Reaction 1: $\text{N}_2(g) + 3\text{H}_2(g) \rightleftharpoons 2\text{NH}_3(g)$, $\Delta H = -x\,\text{kJ mol}^{-1}$. Table 2.1 gives the conditions used to make three equilibrium mixtures, A, B and C.
(a)[1]

Describe and explain any change in the percentage yield of $\text{NH}_3(g)$ formed in B relative to A.

(b(i))[1]

Describe and explain any change in the percentage yield of $\text{NH}_3(g)$ formed in C relative to A.

(b(ii))[2]

Describe and explain the change in the rate of the forward reaction that happens to establish the equilibrium in C compared with A. You do not need to refer to the Boltzmann distribution in your answer.

(c(i))[2]

Write the equilibrium constant expression, $K_p$, for reaction 1. State the units.

(c(ii))[2]

Equilibrium mixture D is formed when $1.0\ \text{mol}$ of $\text{N}_2(g)$ and $3.0\ \text{mol}$ of $\text{H}_2(g)$ are introduced into a sealed container at $750\ ^\circ\text{C}$ and $1000\ \text{atm}$ and allowed to reach equilibrium. This mixture contains $1.16\ \text{mol}$ of $\text{NH}_3(g)$. Calculate the mole fraction of $\text{NH}_3(g)$ in D.

(c(iii))[1]

The mole fraction of $\text{N}_2(g)$ is $0.625$ in a new equilibrium mixture, E. Calculate the partial pressure of $\text{N}_2(g)$ in E when the total pressure is $1000\ \text{atm}$.

(d(i))[3]

Identify the role of $\text{NO}$ and $\text{NO}_2$ in the formation of $\text{H}_2\text{SO}_4$ from $\text{SO}_2$ in the atmosphere so that acid rain is produced. Use relevant equations to support your answer.

(d(ii))[2]

Outline how $\text{NO}$ and $\text{NO}_2$ may help to form photochemical smog.

Worked solution & mark scheme

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