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Enthalpy and entropy

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Question 14

This question is about chemical equilibrium.

Sulfur dioxide, SO2\text{SO}_2SO2​, and oxygen, O2\text{O}_2O2​, react to form sulfur trioxide, SO3\text{SO}_3SO3​, in the reversible reaction shown below:

2SO2(g)+O2(g)⇌2SO3(g)ΔH=−197 kJ mol−1,  ΔS=−188 J mol−1 K−1 2\text{SO}_2(\text{g}) + \text{O}_2(\text{g}) \rightleftharpoons 2\text{SO}_3(\text{g}) \quad \Delta H = -197\text{ kJ mol}^{-1}, \; \Delta S = -188\text{ J mol}^{-1}\text{ K}^{-1} 2SO2​(g)+O2​(g)⇌2SO3​(g)ΔH=−197 kJ mol−1,ΔS=−188 J mol−1 K−1
a.

A dynamic equilibrium exists in a closed system. State one other feature of a dynamic equilibrium.

[1]
b.

Show that the formation of SO3\text{SO}_3SO3​ is feasible at 25∘C25^\circ\text{C}25∘C.

[2]
c.

Determine the maximum temperature, in K\text{K}K, for feasibility. Give your answer to an appropriate number of significant figures.

[2]
d.

A chemist mixes together 2.00 mol of SO2(g)\text{SO}_2(\text{g})SO2​(g) and 1.50 mol of O2(g)\text{O}_2(\text{g})O2​(g) in a container, and the mixture is allowed to reach equilibrium. At equilibrium, 80% of the SO2(g)\text{SO}_2(\text{g})SO2​(g) has been converted to SO3(g)\text{SO}_3(\text{g})SO3​(g), and the total pressure is 1.50 MPa.

Calculate KpK_pKp​, in MPa−1\text{MPa}^{-1}MPa−1, for this reaction. Give your answer to 3 significant figures.

[5]
e.

The chemist then repeats the experiment three times. In each experiment, the chemist makes one change but uses the same initial amounts of SO2\text{SO}_2SO2​ and O2\text{O}_2O2​.

Complete the table to show the predicted effect of each change compared with the original experiment. Only use the words greater, smaller, or same.

ChangeKpK_pKp​Equilibrium amount of SO3(g)\text{SO}_3(\text{g})SO3​(g)Initial rate
Temperature increase
Pressure increase
Catalyst added
[3]

Enthalpy and entropy Questions

  1. A Level
  2. /Chemistry
  3. /Enthalpy and entropy