Thermodynamics: chemical equilibrium

Question 1

Give the equation for working out the reaction Gibbs energy, Δ_RG in the gas phase and describe how it relates to the reaction

Answer 1

If Δ_RG < 0 the forward reaction is spontaneous.

If Δ_RG > 0 the reverse reaction is spontaneous

If Δ_RG = 0 the reaction is at equilibrium.

Question 2

Give the formal definition of the equilibrium constant, K⁰

Answer 2

Note that for this definition, only gaseous species are involved

Question 3

Extend the formal equation of the equilibrium constant to cater for liquid solutions

Answer 3

Note that [J] is the equilibrium concentration of species J

c⁰ is 1moldm^-3

Question 4

Give the equation linking K₀ and Δ_RG⁰

Answer 4

Question 5

Define K⁰

Answer 5

K⁰ is the equilibrium constant which reflects equilibrium composition

If K⁰ is large, products are favoured.

If K⁰ is small, reactants are favoured

Question 6

State Le Chatelier’s principle

Answer 6

A system at equilibrium, when subjected to a disturbance, responds in a way that tends to minimise the effect of the disturbance