DP Chemistry (last assessment 2024)

Question 18M.2.sl.TZ2.5

Date	May 2018	Marks available	[Maximum mark: 3]	Reference code	18M.2.sl.TZ2.5
Level	sl	Paper	2	Time zone	TZ2
Command term	Deduce, Distinguish, Show	Question number	5	Adapted from	N/A

[Maximum mark: 3]

18M.2.sl.TZ2.5

A mixture of 1.00 mol SO₂(g), 2.00 mol O₂(g) and 1.00 mol SO₃(g) is placed in a 1.00 dm³ container and allowed to reach equilibrium.

2SO₂(g) + O₂(g) $\rightleftharpoons$ 2SO₃(g)

(a)

Distinguish between the terms reaction quotient, Q, and equilibrium constant, K_c.

[1]

Markscheme

Q: non-equilibrium concentrations AND K_c: equilibrium concentrations

Q: «measured» at any time AND K_c: «measured» at equilibrium

[1 mark]

(b)

The equilibrium constant, K_c, is 0.282 at temperature T.

Deduce, showing your work, the direction of the initial reaction.

[2]

Markscheme

«Q = $\frac{{{{[{\text{S}}{{\text{O}}_3}]}^2}}}{{{{[{\text{S}}{{\text{O}}_2}]}^2}[{{\text{O}}_2}]}} = \frac{{{{1.00}^2}}}{{{{1.00}^2} \times 2.00}}$ » = 0.500

reverse reaction favoured/reaction proceeds to the left AND Q > K_c/0.500 > 0.282

Do not award M2 without M1.

[2 marks]

Syllabus sections

Core

Core » Topic 7: Equilibrium » 7.1 Equilibrium

Core » Topic 7: Equilibrium

Question 18M.2.sl.TZ2.5

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