Can the value of E°cell be zero? If it is tell me when

Question

This is a chemistry question from electrochemistry.

Answer 1

It can be zero in two instances, First, if you are talking about specifically a half-reaction or half-cell, the standard reduction potential for hydrogen is zero.  This is a defined reference point used in electrochemistry, and it is sometimes called the "Standard Hydrogen Electrode".  The E^o_cell for this half-reaction is zero, and you can find this in any table of standard reduction potentials.

 

The second case would be for a full redox cell or battery involving two half-reactions. For a redox cell with both reduction and oxidation processes to be zero, the E^o_cell for the reduction half-cell has to be exactly equal and opposite the E^o_cell for the oxidation half-cell.  Therefore, when you combine these values to find the E^o_cell for the overall cell, the net result will be zero! 

 

An E^o_cell of zero means that the cell is at equilibrium, and there is no net "forward" or "reverse" EMF.  The reaction will not go spontaneously in either direction.