Equilibrium constant $K_p$ for homogeneous systems (A-level only)

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Question 13
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This question is about some gas mixtures at equilibrium.

This reaction can be used to produce hydrogen iodide:

H2(g)+I2(g)⇌2HI(g)ΔH=−9.4 kJ mol−1\text{H}_2(\text{g}) + \text{I}_2(\text{g}) \rightleftharpoons 2\text{HI}(\text{g}) \quad \Delta H = -9.4\text{ kJ mol}^{-1}H2​(g)+I2​(g)⇌2HI(g)ΔH=−9.4 kJ mol−1

A mixture of 2.50 mol2.50\text{ mol}2.50 mol of H2(g)\text{H}_2(\text{g})H2​(g) and 2.50 mol2.50\text{ mol}2.50 mol of I2(g)\text{I}_2(\text{g})I2​(g) is allowed to reach equilibrium at a constant temperature in a 10 dm310\text{ dm}^310 dm3 container.

At equilibrium, there are 3.60 mol3.60\text{ mol}3.60 mol of HI(g)\text{HI}(\text{g})HI(g).

1.1.

Calculate the mole fraction of HI(g)\text{HI}(\text{g})HI(g) in the equilibrium mixture.

[2]
1.2.

State why the equilibrium constant (KpK_{\text{p}}Kp​) for this reaction has no units.

[1]
1.3.

The temperature of the equilibrium mixture is increased. How does the amount of HI(g)\text{HI}(\text{g})HI(g) change when the new position of equilibrium is reached? Select one:

  • The amount decreases.
  • The amount does not change.
  • The amount increases.
[1]
2.1.

Phosgene can be synthesized from carbon monoxide and chlorine:

CO(g)+Cl2(g)⇌COCl2(g)ΔH=−108 kJ mol−1\text{CO}(\text{g}) + \text{Cl}_2(\text{g}) \rightleftharpoons \text{COCl}_2(\text{g}) \quad \Delta H = -108\text{ kJ mol}^{-1}CO(g)+Cl2​(g)⇌COCl2​(g)ΔH=−108 kJ mol−1

The table below shows the mole fractions of each gas in an equilibrium mixture at a total pressure of 4000 kPa4000\text{ kPa}4000 kPa.

GasMole fraction
Carbon monoxide, CO\text{CO}CO0.5200.5200.520
Chlorine, Cl2\text{Cl}_2Cl2​0.4100.4100.410
Phosgene, COCl2\text{COCl}_2COCl2​0.07000.07000.0700

Give an expression for KpK_{\text{p}}Kp​ for this reaction.

[1]
2.2.

Calculate the value of KpK_{\text{p}}Kp​ at 4000 kPa4000\text{ kPa}4000 kPa. State the units.

[3]
2.3.

State the effect, if any, of an increase in the volume of the container on the value of KpK_{\text{p}}Kp​ for this reaction at a constant temperature.

[1]

Equilibrium constant $K_p$ for homogeneous systems (A-level only) Questions

  1. A Level
  2. /Chemistry
  3. /Equilibrium constant $K_p$ for homogeneous systems (A-level only)