Question

Consider the following galvanic cell with 0.10 M concentrations. The cathode beaker has Ag^+ and NO3^- ions in it. THere is an Ag rod inside it. THe anode beaker has Cu^2+ and SO4^2- in it. There is a Cu bar inside it. K^+ and NO3^- are in the salt bridge. Does cell potential increase,decrease, or remain the same when each of the following changes is made? a) 0.10 M NaCl is added to the cathode compartment. b) 0.10 M NaCl is added to the anode compartment. c) 1.0 M NH3 is added to the cathode compartment. d) 1.0 M NH3 is added to the anode compartment.

Answer 1

First, find the standard cell potential .

     

The reaction will be:

The cell potential is:

If you add sodium chloride to the cathode, silver chloride will precipitate and the concentration of silver ions will decrease.

And the quotient cu/ag will be greater than 1, so the cell potential will decrease.

If you add sodium chloride to the anode, the concentration of copper ions will be the same because copper chloride is soluble. So, the cell potential will be the same.

Ammonio produces silver and copper complexes.

So, If you add ammonia to the cathode, silver diamine complex is formed and the concentration of silver ions will decrease. So, the cell potential will decrease.

If you add ammonio to the anode, copper tetramine complex is formed and the concentration of copper ions will dicrease. So, the cell potential will increase.