Will cell  generate  emf  when  concentration …

The question refers to electrolyte - concentration cells which consist of identical electrodes but are dipped in solutions  of  same  electrolyte having different concentrations. Electrical energy given out by the cell is due to tendency of the electrolyte to diffuse from a solution of higher  concentration to that of lower concentration. Thus two concentrations of the same electrolyte tend to become equal with the expiry of time.  An equilibrium is established at this  stage. This results into a cell emf which happens to be maximum at the start  and then gradually falls to zero.The cell   representation of this cell is  ,

M | M⁺ (C₁) || M⁺  (C₂) | M   ,  

where ,  C₁   &  C₂  are the concentrations  of  the same electrolyte in the two half cells  ,  and  also    C₂ >  C₁

A simple example of such a cell  is  

( Zn|Zn²⁺ (C₁) /  Anode || Zn²⁺  (C₂ )  | Zn / Cathode

The emf  of such a cell is given by using Nernst equation 

E Cell   =  {tex}\frac{0.0591}{n}{/tex} log ( C₁ / C₂  )

When C₁   becomes equal to C₂   E cell  = 0

So , for every concentration cell  E^o   =   0

Thus  ,  the cell will not generate emf  when concentrations  become equal