3.1.6 Chemical equilibria, Le Chatelier’s principle and Kc

Question 1

What are the conditions of a reversible reaction at equilibrium?

Answer 1

• forward and reverse reactions proceed at equal rates
• the concentrations of reactants and products remain constant

Question 2

What is Le Chatelier’s principle?

Answer 2

If a reaction at equilibrium is subjected to a change in conditions (pressure, temperature or concentration) the position of the equilibrium will move to counteract the change

Question 3

Name a use for Le Chatelier’s principle and its what conditions need to be met for the principle to apply?

Answer 3

Le chatelier’s principle can be used to find out the positioning of the equilibrium after a change in condition
For Le Chatelier’s principle to apply the reaction needs to be homologous (all species are in the same state)

Question 4

What effect does a catalyst have on the position of the equilibrium?

Answer 4

A catalyst does not affect the position of the equilibrium

Question 5

Why might a compromise temperature and pressure and temperature be used for reversible reactions in industrial processes?

Answer 5

This is because there are conflicting goals between maximising yield, cost and rate of reaction

Question 6

What is K c ?

Answer 6

Equilibrium constant

Question 7

Formula for K c (Equilibrium constant)?

Answer 7

K c = (concentration of product 1)(concentration of product 2)/ (concentration of reactant 1)(concentration of product 2)

Question 8

What is the only variable that if changed will affect K c and why?

Answer 8

Temperature
because if the temperature of the system is changed, the equilibrium concentrations will also change