Chemistry 2e · 13.3 Shifting Equilibria: Le Châtelier’s Principle

Shifting Equilibria: Le Châtelier’s Principle: practice problems

10 problems from the book, with its answers. Check your working, or have any of them explained to you on the whiteboard.

Exercises 31
The following equation represents a reversible decomposition:
$CaCO_{3} (s) ⇌ CaO (s) + CO_{2} (g)$
Under what conditions will decomposition in a closed container proceed to completion so that no CaCO₃ remains?
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Exercises 33
What property of a reaction can we use to predict the effect of a change in temperature on the value of an equilibrium constant?
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Exercises 34
The following reaction occurs when a burner on a gas stove is lit:
$CH_{4} (g) + 2 O_{2} (g) ⇌ CO_{2} (g) + 2 H_{2} O (g)$
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Exercises 36
Suggest four ways in which the concentration of hydrazine, N₂H₄, could be increased in an equilibrium described by the following equation:
$N_{2} (g) + 2 H_{2} (g) ⇌ N_{2} H_{4} (g) Δ H = 95 kJ$
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Exercises 38
How will an increase in temperature affect each of the following equilibria? How will a decrease in the volume of the reaction vessel affect each?
(a) $2 NH_{3} (g) ⇌ N_{2} (g) + 3 H_{2} (g) Δ H = 92 kJ$
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Exercises 40
Methanol can be prepared from carbon monoxide and hydrogen at high temperature and pressure in the presence of a suitable catalyst.
(a) Write the expression for the equilibrium constant (K $_{c}$ ) for the reversible reaction
$2 H_{2} (g) + CO (g) ⇌ CH_{3} OH (g) Δ H = - 90.2 kJ$
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Exercises 42
Water gas, a mixture of H₂ and CO, is an important industrial fuel produced by the reaction of steam with red hot coke, essentially pure carbon.
(a) Write the expression for the equilibrium constant for the reversible reaction
$C (s) + H_{2} O (g) ⇌ CO (g) + H_{2} (g) Δ H = 131.30 kJ$
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Exercises 44
Ammonia is a weak base that reacts with water according to this equation:
$NH_{3} (a q) + H_{2} O (l) ⇌ NH_{4}^{+} (a q) + OH^{-} (a q)$
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Exercises 46
Suggest two ways in which the equilibrium concentration of Ag⁺ can be reduced in a solution of Na⁺, Cl⁻, Ag⁺, and $NO_{3}^{-},$ in contact with solid AgCl.
$Na^{+} (a q) + Cl^{-} (a q) + Ag^{+} (a q) + NO_{3}^{-} (a q) ⇌ AgCl (s) + Na^{+} (a q) + NO_{3}^{-} (a q)$
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Exercises 48
A solution is saturated with silver sulfate and contains excess solid silver sulfate:
$Ag_{2} SO_{4} (s) ⇌ 2 Ag^{+} (a q) + SO_{4}^{2 -} (a q)$
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Key terms · 1

Le Châtelier’s principle: an equilibrium subjected to stress will shift in a way to counter the stress and re-establish equilibrium

Learn 13.3 on the whiteboard

The tutor teaches the whole section, drawing it out step by step and answering your questions as you go.

Read 13.3 in the textbook · This section on openstax.org

Shifting Equilibria: Le Châtelier’s Principle: practice problems

10 problems from the book, with its answers. Check your working, or have any of them explained to you on the whiteboard.

Exercises 31

The following equation represents a reversible decomposition:

$CaCO_{3} (s) ⇌ CaO (s) + CO_{2} (g)$

Under what conditions will decomposition in a closed container proceed to completion so that no CaCO₃ remains?

Exercises 33

What property of a reaction can we use to predict the effect of a change in temperature on the value of an equilibrium constant?

Exercises 34

The following reaction occurs when a burner on a gas stove is lit:

$CH_{4} (g) + 2 O_{2} (g) ⇌ CO_{2} (g) + 2 H_{2} O (g)$

Exercises 36

Suggest four ways in which the concentration of hydrazine, N₂H₄, could be increased in an equilibrium described by the following equation:

$N_{2} (g) + 2 H_{2} (g) ⇌ N_{2} H_{4} (g) Δ H = 95 kJ$

Exercises 38

How will an increase in temperature affect each of the following equilibria? How will a decrease in the volume of the reaction vessel affect each?

(a) $2 NH_{3} (g) ⇌ N_{2} (g) + 3 H_{2} (g) Δ H = 92 kJ$

Exercises 40

Methanol can be prepared from carbon monoxide and hydrogen at high temperature and pressure in the presence of a suitable catalyst.

(a) Write the expression for the equilibrium constant (K $_{c}$ ) for the reversible reaction

$2 H_{2} (g) + CO (g) ⇌ CH_{3} OH (g) Δ H = - 90.2 kJ$

Exercises 42

Water gas, a mixture of H₂ and CO, is an important industrial fuel produced by the reaction of steam with red hot coke, essentially pure carbon.

(a) Write the expression for the equilibrium constant for the reversible reaction

$C (s) + H_{2} O (g) ⇌ CO (g) + H_{2} (g) Δ H = 131.30 kJ$

Exercises 44

Ammonia is a weak base that reacts with water according to this equation:

$NH_{3} (a q) + H_{2} O (l) ⇌ NH_{4}^{+} (a q) + OH^{-} (a q)$

Exercises 46

Suggest two ways in which the equilibrium concentration of Ag⁺ can be reduced in a solution of Na⁺, Cl⁻, Ag⁺, and $NO_{3}^{-},$ in contact with solid AgCl.

$Na^{+} (a q) + Cl^{-} (a q) + Ag^{+} (a q) + NO_{3}^{-} (a q) ⇌ AgCl (s) + Na^{+} (a q) + NO_{3}^{-} (a q)$

Exercises 48

A solution is saturated with silver sulfate and contains excess solid silver sulfate:

$Ag_{2} SO_{4} (s) ⇌ 2 Ag^{+} (a q) + SO_{4}^{2 -} (a q)$

Key terms · 1

Le Châtelier’s principle: an equilibrium subjected to stress will shift in a way to counter the stress and re-establish equilibrium

Learn 13.3 on the whiteboard

The tutor teaches the whole section, drawing it out step by step and answering your questions as you go.

Read 13.3 in the textbook · This section on openstax.org