Question

Calculate E_cell and ΔG for the following at 28°C : 

Mg_(s) + Sn²⁺ (0.04M) → Mg²⁺(0.06M) + Sn_(s)

E⁰_cell = 2.23 V 

Is the reaction spontaneous?

Answer 1

Given :

Mg_(s) + Sn²⁺ (0.04M) → Mg²⁺(0.06M) + Sn_(s)

[Sn²⁺] = 0.4 M 

[Mg²⁺] = 0.06 M

E⁰_cell = 2.23 V 

E_cell = ?

ΔG = ?

2.23 – 0.0296 × 0.1761 

= 2.23 – 0.005213 

= 2.224V

ΔG = – nFE 

= – 2 × 96500 × 2.224 

= – 4.292 × 105 J 

= - 429.2 kJ

Since ΔG is negative, 

The electrochemical reaction is spontaneous.