Question

[Ag(NH₃)₂]⁺ (aq) + e^- $\rightarrow$ Ag(s) + 2 NH₃ (aq) E ^{$^{\circ}$} = +0.373V

Use the standard redox potential of silver below to calculate the stability constant of the silver diamine complex.

Ag⁺ + e^- $\rightarrow$ Ag(s) E ^{$^{\circ}$} ?= +0.7996V

Would you expect the redox potential to increase or decrease if NH₃ is replaced with pyridine? Explain your answer

Answer 1

Ag ⁺ + e^- $\rightarrow$ Ag (S) E $^{\circ}$ ​= +0.7996V

[Ag(NH₃)₂⁺] (aq) + e^- $\rightarrow$ Ag(s) + 2 NH₃ (aq)    E $^{\circ}$ = +0.373V

Hence overall reaction is

Ag ⁺ +  2 NH₃ (aq) $\rightarrow$ [Ag(NH₃)₂⁺] (aq)

E^o Cell = E^o cathode - E^o anode = 0.7996V- 0.373V= 0.4266V

Further E^o = 0.0591 log k

log k = 0.4266V/ 0.0591 = 7.22 , therefore

Staility constant k= 1.6 x 10⁷