Equilibria

Explain the term homogeneous equilibrium

Reactants and products have same state symbol.[cite: 27]

Explain the term heterogeneous equilibrium

Reactants and products have different state symbols.[cite: 27]

Explain the conditions required for a dynamic equilibrium to be established

Closed system; rate of forward reaction = rate of reverse reaction; concentrations of all species remain constant.[cite: 27]

Position of equilibrium (Le Chatelier's Principle): Describe and explain the effect of increasing the concentration of A on A + B ⇌ C + D

Equilibrium position will shift to the right (A + B -> C + D).[cite: 27]

Position of equilibrium: Describe and explain the effect of increasing the pressure on 2A + 3B ⇌ C + 2D

Equilibrium position will shift to the right (2A + 3B -> C + 2D) because there are fewer moles of gas on the right (product) side (3 moles vs 5 moles).[cite: 27]

Position of equilibrium: Describe and explain the effect of increasing the pressure on 2A + 3B ⇌ 2C + 3D

Equilibrium position does not change because there are the same number of moles of gas on each side of the equation (5 moles vs 5 moles).[cite: 27]

Describe and explain the effect of increasing the temperature on the position of equilibrium for A + B ⇌ C + D (ΔH = -53 kJ mol⁻¹)

Equilibrium position will shift to the left (C + D -> A + B) because the reverse reaction is endothermic.[cite: 26]

Describe and explain the effect of adding a catalyst on the position of equilibrium

The equilibrium position does not change; rate of forward and reverse reactions is increased equally; the value of Kc / Kp does not change.[cite: 26]

Explain the conditions for maximum yield and how industrial conditions may vary for the Haber synthesis of ammonia (N2(g) + 3H2(g) ⇌ 2NH3(g), ΔH = -92 kJ mol⁻¹)

Maximum yield: High pressure (shifts equilibrium right due to fewer gas moles on product side) and low temperature (shifts equilibrium right as forward reaction is exothermic). Compromise conditions: Pressure is compromised as extremely high pressures are too dangerous; temperature is compromised because if too low, rate of reaction is too slow; Fe catalyst is used to lower energy demand and CO2 emissions.[cite: 25]

Explain why it is difficult to predict how increasing both temperature and pressure affects the amount of NH3 formed at equilibrium

Increased pressure shifts equilibrium to the right (fewer gas moles on product side); higher temperature shifts equilibrium to the left (reverse reaction is endothermic); difficult to predict which of the two opposing factors has the greatest contribution.[cite: 25]