Chemistry 9701 · AS & A Level · Atoms, molecules and stoichiometry

Atoms, molecules and stoichiometry — practice question

Methanol, $\text{CH}_3\text{OH}$, is manufactured industrially by allowing carbon monoxide, $\text{CO}$, to react with hydrogen, $\text{H}_2$. $\text{CO(g)} + 2\text{H}_2\text{(g)} \rightleftharpoons \text{CH}_3\text{OH(g)} \qquad \Delta H = -91\ \text{kJ mol}^{-1}$. This process is operated at $4 \times 10^3\ \text{kPa}$ (40 atmospheres) and $1150\ \text{K}$.
(a(i))[2]

State what Le Chatelier’s Principle says.

(a(ii))[4]

Using your knowledge of Le Chatelier’s Principle, state the temperature and pressure conditions that could be used to produce a greater yield of methanol in this process. For each condition, explain why the yield would rise.

(b)[4]

The carbon monoxide used to make methanol may be produced by reacting carbon dioxide with hydrogen. $$\text{CO}_2\text{(g)} + \text{H}_2\text{(g)} \rightleftharpoons \text{CO(g)} + \text{H}_2\text{O(g)}$$ $$K_c = 1.44\ \text{at}\ 1200\ \text{K}$$ A mixture containing $0.70\ \text{mol}$ of $\text{CO}_2$, $0.70\ \text{mol}$ of $\text{H}_2$, $0.30\ \text{mol}$ of $\text{CO}$ and $0.30\ \text{mol}$ of $\text{H}_2\text{O}$ was put into a $1\ \text{dm}^3$ flask and left to reach equilibrium at $1200\ \text{K}$. Calculate the amount, in moles, of each substance in the equilibrium mixture at $1200\ \text{K}$.

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