Question

The standard free energy of formation of the aqueous complex ion Cd(NH3)42+ is -226.1 kJ mol-1. The free energy of formation of NH3 is -26.50 kJ mol-1 and that of the Cd2+ ion is -77.61 kJ mol-1. The value of the stability constant for the complex ion Cd(NH3)42+ is:
(a) 2.14 x 105
(b) 2.84 x 105
(c) 5.28 x 10-5
(d) 2.78 x 107

Answer 1

The stability constant for the complx is
Cd^+2 + 4NH3 ==> Cd(NH4)3^+2

Kstab = [Cd(NH3)4^+2]/(Cd^+2)(NH3)^4

delta Gorxn = [delta Go products\-[delta Go reactants]. Then delta Gorxb = -RTlnK and solve for lnK.