FRQ — Equilibrium

Case study·Standard multi-step (3/5)·Calculator allowed

Difficulty guide

The label describes the problem, not your ability.

1/5 - Foundational

Warm-up setup; checks one basic idea.

2/5 - Routine exam skill

Normal syllabus skill; usually one main rule or interpretation.

3/5 - Standard multi-step

Exam-style problem with multiple steps or a common trap.

4/5 - Hard exam skill

High-end exam problem; combines methods carefully.

5/5 - Challenge

Stretch problem beyond normal exam pressure.

Question

A sealed vessel contains

\mathrm{A(g)}

and

\mathrm{B(g)}

forming

\mathrm{C(g)}

reversibly. At

500\text{ K}

K_c=12

. Three trial mixtures have

Q_c=4

12

and

20

respectively.

Total: 5 marks

(a) State the direction of shift for $Q_c=4$ . (1 mark)

(b) State the direction of shift for $Q_c=12$ . (1 mark)

(d) Explain why $K_c$ is not changed by choosing a different trial mixture at the same temperature. (2 marks)

Your response (optional — you can also work on paper)

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