Heat of Reaction in an Electrochemical Cell
Let n Faraday charge flows out of a cell of emf E, then
…….(i)
Gibbs – Helmholtz equation from thermodynamics may be given as
…….(ii)
From equation (i) and (ii) we get,
where 
= Temperature coefficient of cell
Case I: When 
= 0, then 
Case II: When 
> 0, then 
i.e. process inside the cell is endothermic.
Case III: When < 0, then 
i.e., process inside the cell is exothermic.