Determine the standard Gibbs energy change at 298 K for the reaction
2Ag⁺ (aq) + Zn(s) $\rightarrow$ 2Ag(s) + Zn²⁺(aq)
Using the data for the standard reduction potentials in Table 16.2.

Question

Determine the standard Gibbs energy change at 298 K for the reaction 2Ag⁺ (aq) + Zn(s) $\rightarrow$2Ag(s) + Zn²⁺(aq) Using the data for the standard reduction potentials in Table 16.2.

Quizplus · Accepted Answer

First, we need to write the half-reactions for the oxidation and reduction reactions involved in the overall reaction:

Ag2S(s) + 2e- -> 2Ag(s) + S2-(aq)        E° = -0.92 V
Zn(s) -> Zn2+(aq) + 2e-                          E° = -0.76 V
2H2S(aq) + 2e- -> S2-(aq) + 2H+(aq)     E° = +0.14 V

Now, we can combine the half-reactions to obtain the overall reaction and its standard potential:

2Ag2S(s) + Zn(s) + 4H+(aq) -> 4Ag(s) + ZnS2(s) + 2H2S(aq)              E° = -1.68 V

Since ΔG° = -nFE°, where n is the number of moles of electrons transferred and F is the Faraday constant, we can calculate the standard Gibbs energy change using:

ΔG° = -nFE° = -8 mol x (-96485 C/mol) x (-1.68 J/C) / 1000 J/kJ = -301.2 kJ/mol

The best choice is B.

Determine the Standard Gibbs Energy Change at 298 K for the Reaction