Question

Consider a voltaic (galvanic) cell with the following metal electrodes. Identify which metal is the cathode and which is the anode, and calculate the cell potential. (Use the table of Standard Electrode Potentials.)

(a)    Co(II) and Sn(II)
Cathode:

Co(II) or Sn(II)   

Anode:

Co(II) or Sn(II)   

E_cell =   ???????

(b)    Sc(III) and Cd(II)
Cathode:

Sc(III)or Cd(II)    

Anode:

Sc(III) or Cd(II)    

E_cell = ??????V

(c)    Al and Zr(IV)
Cathode:

Al or Zr(IV)    

Anode:

Al or Zr(IV)    

E_cell = ????????? V

Answer 1

The cell with higher standard reduction potential will undergo
reduction at anode
The half cell with lower reduction potential value will
undergo oxidation at anode
E0cell = E0cathode-E0anode
Co2+. Sn2+
Co2+ + 2 e−   -->Co(s)   −0.28 V
Sn2+ + 2 e−--> Sn(s)   −0.13 V

Anode is Co/Co2+

Cathode is Sn2+/Sn

Ecell = Ecathode- Eanode= -0.13 V- [-0.28 V] =
=0.15 V
********************

Sc3+, Cd2+
Sc3+ + 3 e−   -->   Sc(s)     −2.077
Cd2+ + 2 e−   -->   Cd(s)   −0.40
Anode is Sc/Sc3+

Cathode is Cd2+/Cd

Ecell = Ecathode- Eanode= -0.40 v-[-2.077V]= 1.677 V
*****************

Al and Zr4+
Al3+ + 3 e−   -->   Al(s)   −1.662 V
Zr4+ + 4 e−   --->   Zr(s)   −1.45V

Anode is Al/Al3+

Cathode is Zr4+/Zr

Ecell = Ecathode- Eanode= -1.45 V- [-1.662 V]
= 0.212 V