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Edexcel A Level Chemistry

Topic 10
Equilibrium I

Topic 10 covers reversible reactions and dynamic equilibrium, Le Chatelier’s principle for temperature, concentration and pressure, the compromise between yield and rate in industrial processes, and writing the expression for the equilibrium constant Kc for homogeneous and heterogeneous systems. Equilibrium II (Kc and Kp calculations) follows in Topic 11.

Exam Paper
Paper 1
9CH0/01
Specification Points
10.1 – 10.4
4 points covered
Topic Parts
4 pages
Revision notes available
Exam Board
Edexcel
Pearson 9CH0

Revision Notes

Reversible
Dynamic
Equilibrium
rates equal, concentrations constant
1
Available

Dynamic Equilibrium

Dynamic equilibrium: reversible reactions, equal forward and reverse rates, constant concentrations, closed systems and the position of equilibrium.

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Shifts
Le Chatelier’s
Principle
temperature, pressure, concentration
2
Available

Le Chatelier’s Principle

Le Chatelier’s principle: temperature, pressure and concentration changes, catalysts, and the ammonia and chromate equilibria as examples.

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Yield versus rate
Equilibria in
Industry
Haber, Contact, compromise
3
Available

Equilibria in Industry

Equilibria in industry: the Haber and Contact processes, compromise temperature and pressure, catalysts and evaluating yield data.

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Products over reactants
Equilibrium
Constant Kc
expression, units, calculation
4
Available

The Equilibrium Constant Kc

Kc: expressions, units, calculations from equilibrium amounts, the magnitude of Kc and the effect of temperature.

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Specification Coverage

Topic 10 Equilibrium I – Edexcel A Level Chemistry

The following specification points outline the knowledge and skills students are expected to demonstrate. Wording follows the Edexcel A Level Chemistry (9CH0) specification.

Equilibrium I

10.1
know that many reactions are readily reversible and that they can reach a state of dynamic equilibrium in which:
i
the rate of the forward reaction is equal to the rate of the backward reaction
ii
the concentrations of reactants and products remain constant
10.2
be able to predict and justify the qualitative effect of temperature, concentration and pressure on a homogeneous equilibrium
10.3
evaluate data to explain the necessity, for many industrial processes, to reach a compromise between the yield and the rate of reaction
10.4
be able to deduce an expression for Kc, for homogeneous and heterogeneous systems, in terms of equilibrium concentrations