At 450 K phosphorus(V) chloride, PCl5(g), decomposes to form phosphorus(III) chloride, PCl3(g), and chlorine, Cl2(g). A dynamic equilibrium is established as shown.
PCl5(g) ⇌ PCl3(g) + Cl2(g) ΔH = +124 kJ mol-1
When 2.00 mol of PCl5(g) are decomposed at 450K and 1.00 × 10^5 Pa the resulting equilibrium mixture contains 0.800 mol of Cl2(g).

Q: What topic does this question test?

This question tests Equilibria in A-Level Chemistry (syllabus code 9701). It is worth 12 marks.

Q: Which exam paper is this question from?

This question appeared in the Cambridge A-Level Chemistry Oct/Nov 2017 examination, Paper 2 Variant 2 (9701_w17_qp_22.pdf).

Question

At 450 K phosphorus(V) chloride, PCl5(g), decomposes to form phosphorus(III) chloride, PCl3(g), and chlorine, Cl2(g). A dynamic equilibrium is established as shown.
PCl5(g) ⇌ PCl3(g) + Cl2(g) ΔH = +124 kJ mol-1
When 2.00 mol of PCl5(g) are decomposed at 450K and 1.00 × 10^5 Pa the resulting equilibrium mixture contains 0.800 mol of Cl2(g).

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