Question

When will we get maximum work done in galvanic cells?

Answer 1

Maximum work of a galvanic cell is equal to gibb's free energy of the cell.

ΔG = -wmax

ΔG can be calculated as 

ΔG = nF Ecell

So, when E.M.F of the cell is maximum, then the Gibb's free energy will be maximum, and thus, work obatined from the cell will be maximum.

Hope its clear now.

Enjoy learning!!

Answer 2

Hi!

A question from NCERT.

 If concentration of all reacting species is unity, then Ecell=E°cell and ΔG°=-nFE°cell  Where, ΔG is standard Gibbs energy of the reaction E°cell= emf of the cell, nF = charge passed. If we want to obtain maximum work from a galvanic cell then charge has to be passed reversibly. The reversibly work done by a galvanic cell is equal to decrease in its Gibbs energy. As  is an intensive parameter but A,. G is an extensive thermodynamic property and the value depends on n. For reaction, Zn+Cu2+-->Zn2+ + Cu in a galvanic cell. ΔG=-2FE°cell, [Here, n = 2]

Hope it will help. Thank you.