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IB Chemistry SL 2.3 Extent of Chemical Change Question Bank

Practise IB Chemistry SL 2.3 with questions on dynamic equilibrium, K expressions, equilibrium position and Le Châtelier’s principle.

Syllabus
First assessment 2025
Course
Chemistry SL
Level
SL

Covered syllabus points

2.3.1—Dynamic equilibrium2.3.2—Equilibrium law2.3.3—Equilibrium constant (K)2.3.4—Le Châtelier's principle

2.3 Extent of chemical change question 1

[Maximum number: 5]

Question (a)

(a)

Describe two characteristics of a reaction at equilibrium.

[ 2 ]

Question (b)

(b)

State and explain the effect of a catalyst on the position of equilibrium.

[ 2 ]

Question (c)

(c)

Ethanoic acid reacts with ethanol to form the ester ethyl ethanoate.

CH3COOH(l)+CH3CH2OH(l)⇌H+CH3COOCH2CH3(l)+H2O(l)\mathrm{CH}_{3} \mathrm{COOH}(\mathrm{l})+\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}(\mathrm{l}) \stackrel{\mathrm{H}^{+}}{\rightleftharpoons} \mathrm{CH}_{3} \mathrm{COOCH}_{2} \mathrm{CH}_{3}(\mathrm{l})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l})

The esterification reaction is exothermic. State the effect of increasing temperature on the value of the equilibrium constant ( KcK_{\mathrm{c}} ) for this reaction.

[ 1 ]

2.3 Extent of chemical change question 2

[Maximum number: 2]

The reaction between ethanoic acid and ethanol is homogeneous and reversible.

C2H6O(l)+C2H4O2(l)⇌C4H8O2(l)+H2O(l)ΔHθr=−4 kJ mol−1\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}(\mathrm{l})+\mathrm{C}_{2} \mathrm{H}_{4} \mathrm{O}_{2}(\mathrm{l}) \rightleftharpoons \mathrm{C}_{4} \mathrm{H}_{8} \mathrm{O}_{2}(\mathrm{l})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \quad \Delta H^{\theta}{ }_{\mathrm{r}}=-4 \mathrm{~kJ} \mathrm{~mol}^{-1}

Question (a)

(a)

Deduce the expression for the equilibrium constant, K, for this reaction.

[ 1 ]

Question (b)

(b)

Explain the effect of reducing the temperature on the value of the equilibrium constant.

[ 1 ]
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