Question

Write the expressions for the equilibrium constants of the following reactions, that includes the mass action relationships (i.e., the ratio of standardized partial pressures) and the value of the equilibrium constant calculated from the Gibbs energies of reaction:

a) CO₂(g)+Cl₂(g) <->COCl(g)+Cl(g)

b)2SO₂(g)+)O₂(g) <-> 2SO₃(g)

c)H₂(g)+Br₂(g) <-> 2HBr(g)

d)2O₃(g) <-> 3O₂(g)

Answer 1

Equilibrium constant at constant pressure, Kp is expressed as ratio of the product of partial pressures of the products to that of the reactants raised to a power equal to the coefficient in the balanced equation.  

(a): CO(g)+Cl₂(g) <->COCl(g)+Cl(g)

Kp = [P_COCl(g)* P_Cl(g)] / [P_CO(g)* P_Cl(g)]

where P_COCl(g) = Partial pressure of COCl(g)

P_Cl2(g) = Partial pressure of Cl2(g)

P_CO(g) = Partial pressure of CO(g)

P_Cl(g) = Partial pressure of Cl(g)

(b): 2SO₂(g)+O₂(g) <---> 2SO₃(g)

Kp = [P_SO3(g)]² / ([P_SO2(g)]² * P_O2(g)) ​​​​​​

where P_SO3(g) = Partial pressure of SO₃(g)

P_O2(g) = Partial pressure of O₂(g)

P_SO2(g) = Partial pressure of SO₂(g)

(c): H₂(g)+ Br₂(g) <---> 2HBr(g)

Kp = [P_HBr(g)]² / (P_H2(g) * P_Br2(g)) ​​​​​​

where P_HBr(g) = Partial pressure of HBr(g)

P_H2(g) = Partial pressure of H₂(g)

P_Br2(g) = Partial pressure of Br₂(g)

(d): 2O₃(g) <----> 3O₂(g)

Kp = [P_O2(g)]³ / [P_O3(g)]² ​​​​​​

where P_O2(g) = Partial pressure of O₂(g)

P_O3(g) = Partial pressure of O₃(g).