Calculate the EMF:

Problem: Calculate the EMF of the following electrochemical cell at 25°C: 

Answer:

The half-cell reactions are :

R.H.E.  2H⁺ + 2e^-    ↔  H2 (g)

L.H.E.  Cu (s) ↔     Cu²⁺ (aq) + 2e^-

Overall reaction : Cu(s) + 2H⁺   ↔    Cu²⁺ (aq) + H₂ (g)

E°_cell = E° = E°R - E°L = - 0.34 V

The EMF of the cell is given by,

E = E° -( 0.0591/2) log a_cu²⁺ × a_H2/(a_H⁺)² at 25ºc

=- 0.337 -( 0.0591/2) log (0.1) (0.95)/ (0.01)²

= - 0.337 - 0.088 = - 0.425 V