Chemistry 0620 · IGCSE · Reversible reactions and equilibrium
Reversible reactions and equilibrium — practice question
Hydrogen and iodine undergo a reversible reaction and hydrogen iodide is produced. $\text{H}_2(g) + \text{I}_2(g) \rightleftharpoons 2\text{HI}(g)$. The forward reaction gives out heat. A sealed gas syringe containing an equilibrium mixture of hydrogen, iodine and hydrogen iodide gases was heated to 250^{\circ}C. The equilibrium mixture appeared pale purple.
(a)[2]
What does the term equilibrium mean?
(b(i))[1]
Give a reason for why the equilibrium position stayed the same.
(b(ii))[1]
Suggest why the gas mixture became a deeper purple, even though the equilibrium position stayed the same.
(c(i))[1]
What happened to the equilibrium position when the temperature of the gas syringe was increased from 250^{\circ}C to 300^{\circ}C?
(c(ii))[2]
What happened to the rate of the forward reaction and the rate of the backward reaction when the temperature of the gas syringe was increased from 250^{\circ}C to 300^{\circ}C?
Worked solution & mark scheme
This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: “rate of forward reaction is equal to rate of reverse reaction” …