Question

How does adding NH3 into the cell with CuSO4 affect the voltage measurement? The other cell has ZnSO4

Answer 1

The addition of NH3 to a solution of copper(II) ions causes the formation of the copper ammonia complex, Cu(NH3)4^+2, and this reduces the concentration of the Cu^+2 ion in solution which reduces the voltage of that half cell and of course the voltage of the cell.