Question

Calculate the standard cell potential for each of the following electrochemical cells.

Ni^+2(aq)+Mg(s)--->Ni(s)+Mg^+2(aq)

I used the e cell values from the back of my book. They are:

Ni^+2(aq)+2e--->Ni(s) E^0= -0.23 V
Mg^+2(aq)+2e--->Mg(s) E^0= -2.37

I did E^0= -0.23 - 2.37= -2.60 V ; however, my online hw said that was wrong. Is there another step I'm missing?

Answer 1

Correction:

E_cell= -0.23 - 2.37= -2.60 V

Answer 2

Look at your complete equation.
Ni^+2(aq)+Mg(s)--->Ni(s)+Mg^+2(aq)

Ni^+2 + 2e ==> -0.023 v
Mg(s) ==> Mg^+2 + 2e is the reverse of the cell you looked up; therefore, the voltage for this cell is +2.37. Then Ecell = -0.23 + 2.37 = ??
(You have added a reduction half cell to an oxidation half cell.)

Ni^+2(aq)+2e--->Ni(s) E^0= -0.23 V
Mg^+2(aq)+2e--->Mg(s) E^0= -2.37

Answer 3

2.14 V