Equilibria (AS)：練習題

For the reversible reaction \( \text{N}_2\text{(g)} + 3\text{H}_2\text{(g)} \rightleftharpoons 2\text{NH}_3\text{(g)} \), what happens if the concentration of \( \text{H}_2\text{(g)} \) is increased at constant temperature and pressure?

Consider the reaction: \( \text{2SO}_2\text{(g)} + \text{O}_2\text{(g)} \rightleftharpoons \text{2SO}_3\text{(g)} \quad \Delta H = -197 \text{ kJ mol}^{-1} \).
Which of the following changes will increase the equilibrium yield of \( \text{SO}_3 \)?

The partition coefficient, \( K_{pc} \), of a solute \( X \) between hexane and water is 8.0.
\( K_{pc} = \frac{[X]_{\text{hexane}}}{[X]_{\text{water}}} = 8.0 \)
An aqueous solution contains \( 10.0 \text{ g} \) of \( X \) in \( 100 \text{ cm}^3 \) of water. This solution is shaken with two successive \( 20 \text{ cm}^3 \) portions of hexane. What is the total mass of \( X \) extracted into the hexane layers?

For the reaction \( \text{H}_2\text{(g)} + \text{I}_2\text{(g)} \rightleftharpoons \text{2HI(g)} \), at a certain temperature, 1.0 mol of \( \text{H}_2 \) and 1.0 mol of \( \text{I}_2 \) are placed in a 2.0 dm³ container. At equilibrium, 0.4 mol of \( \text{HI} \) is formed. Calculate the value of \( K_c \).

For the decomposition of dinitrogen tetroxide: \( \text{N}_2\text{O}_4\text{(g)} \rightleftharpoons \text{2NO}_2\text{(g)} \).
At \( 25^\circ\text{C} \), \( K_p = 0.11 \text{ atm} \). At \( 100^\circ\text{C} \), \( K_p = 11 \text{ atm} \).
Which statement about this reaction is correct?

For the reversible reaction:
\(2\mathrm{SO}_2(\mathrm{g}) + \mathrm{O}_2(\mathrm{g}) \rightleftharpoons 2\mathrm{SO}_3(\mathrm{g}) \quad \Delta H = -197 \mathrm{\,kJ\,mol}^{-1}\)

Predict and explain the effect on the position of equilibrium when the pressure is increased.

Explain why a catalyst does not affect the position of equilibrium for a reversible reaction, despite increasing the rate of reaction.

(a) Define pH.

(b) Calculate the pH of a \( 0.020 \text{ mol dm}^{-3} \) solution of hydrochloric acid, \( \text{HCl} \).

(c) Ethanoic acid, \( \text{CH}_3\text{COOH} \), is a weak acid with an acid dissociation constant, \( K_a \), of \( 1.74 \times 10^{-5} \text{ mol dm}^{-3} \) at \( 298 \text{ K} \). Calculate the pH of a \( 0.10 \text{ mol dm}^{-3} \) solution of ethanoic acid.

The reversible reaction between nitrogen and hydrogen to form ammonia is an important industrial process, the Haber process:

\( \text{N}_2\text{(g)} + 3\text{H}_2\text{(g)} \rightleftharpoons 2\text{NH}_3\text{(g)} \quad \Delta H = -92 \text{ kJ mol}^{-1} \)

(a) Explain how a catalyst affects the rate of this reaction and the position of equilibrium.

(b) A mixture of \( 2.0 \text{ mol} \) of \( \text{N}_2 \) and \( 6.0 \text{ mol} \) of \( \text{H}_2 \) is placed in a \( 1.0 \text{ dm}^3 \) container. At equilibrium, \( 3.0 \text{ mol} \) of \( \text{NH}_3 \) are present.

(i) Calculate the number of moles of \( \text{N}_2 \) and \( \text{H}_2 \) present at equilibrium.

(ii) Write the expression for \( K_c \) for this reaction.

(iii) Calculate the value of \( K_c \) at this temperature, stating its units.