Consider the following E° values of given half cell E°Ag^+ / Ag = 0.8 V, E° Zn^2+/Zn = -0.76 V

Question

Consider the following E° values of given half cell 

\(E^\circ _{Ag^+ /Ag} = 0.8 \ V, E^{\circ} _{Zn^{2+} / Zn} = -0.76\ V\)

\(E^\circ _{Cu^{2+} / Cu} = 0.34 \ V, E^\circ _{Mg^{2+}/Mg} = -2.36\ V\)

Then which of the following will have the most negative value of ΔG°? 

(1) Zn|Zn²⁺||Cu²⁺|Cu 

(2) Mg|Mg²⁺||Ag⁺ |Ag 

(3) Mg|Mg²⁺||Zn²⁺|Zn 

(4) Cu|Cu²⁺||Ag²⁺|Ag

Answer 1

Correct option is: (2) Mg|Mg²⁺||Ag⁺ |Ag 

The cell which has most positive value of E°_Cell  will have most negative value of ΔG°.

\(E^\circ _{cell} = E^\circ _{Ag^+| Ag} - E^\circ _{Mg^{2+} | Mg} = 0.8 - (-2.36) = 3.16V\)

\(\Delta G^\circ = -nFE^\circ _{cell}\)