Question

Calculate the standard free energy change for the following reaction

Sn²⁺ (aq) + Fe(s) → Sn(s) +Fe²⁺ (aq)

If E°( Sn²⁺/Sn) = - 0.14 V and E°( Fe²⁺/Fe) = - 0.44 V (Faraday constant 96,500 J/V.mol)

Answer 1

To calculate the standard free energy change;

$- \Delta G^o =nFE_{cell}^o$

$E_{cell}^o= -(-0.44V)- 0.14V = 0.30V\\ F = 96500\ J/V.mol\\ n=2$

$\begin{aligned}- \Delta G^o &=nFE_{cell}^o\\ &= 2× 96500× 0.30\\ &= 57900\ J \approx 57.9\ kJ\\ \end{aligned}$

$\therefore \Delta G^o= -57.9\ kJ$