Equilbrium constant for the reaction
CH3COOH+H2O⇌CH3COO−+H3O+
K1=[CH3COO−][H3O+][CH3COOH][H2O]
Equilibrium constant for the reaction
2H2O⇌H3O++OH−
K2=[H3O+][OH−][H2O]2
Taking the ratio of K1 and K2
K1K2=[CH3COO−][H3O+][CH3COOH][H2O]×[H2O]2[H3O+][OH−]
K1K2=[CH3COO−][H2O][CH3COOH][OH−]
Above ratio is the equilibrium constant of the reaction
CH3COOH+OH−⇌CH3COO−+H2O
∴K=K1K2=1.8×10−51×10−14=1.8×109