CAIE A Level Chemistry 9701 · Equilibria

Equilibria: suggest question

Suggest4 marksStandard

A student places a mixture of hydrogen and iodine vapour in a sealed flask and heats the flask to 450 °C. The gases reach a dynamic equilibrium.

\ce{H2(g) + I2(g) <=> 2HI(g)}

(a) Suggest what is meant by a dynamic equilibrium, in terms of the rates of the forward and reverse reactions. (b) Suggest the expression for the equilibrium constant, $K_c$ , for this reaction. (c) In a separate experiment, the equilibrium mixture is compressed to a smaller volume in a closed container at constant temperature. Suggest what happens to the position of equilibrium, and explain your answer.

How this question is marked

4 marks, so the mark scheme is looking for about 4 separate creditworthy points. Making the same point twice in different words earns it once.

Suggest means: Apply what you know to an unfamiliar situation. There may be more than one acceptable answer. Reason from the principle you have learned to the new context, and say which principle you are using.

Equilibria: suggest question

How this question is marked

More Equilibria questions