Assemble a battery, represented by the diagram below with the cathode in compart

Question

Assemble a battery, represented by the diagram below with the cathode in compartment A, with Mg2+/Mg and Zn2+/Zn couples in which the voltage reads positive. (Use the Standard Reduction Potentials Table. Use the lowest possible coefficients. Omit states-of-matter from your answer.)

STANDRD REDUCTION TABLE:

+2.87

(a) What half-reaction occurs in compartment A?

(b) What half-reaction occurs in compartment B?

(c) Write the net redox reaction.

(d) What is the cell potential?

___________ V

Ox + n e– Red E° (V) K+(aq) + e– K(s) -2.92 Na+(aq) + e– Na(s) -2.71 Mg2+(aq) + 2 e– Mg(s) -2.36 Al3+(aq) + 2 e– Al(s) -1.66 2 H2O(l) + 2 e– H2(g) + 2 OH–(aq) -0.83 Zn2+(aq) + 2 e– Zn(s) -0.76 Fe2+(aq) + 2 e– Fe(s) -0.44 PbSO4(aq) + 2 e– Pb(s) + SO42–(aq) -0.36 Ni2+(aq) + 2 e– Ni(s) -0.23 Sn2+(aq) + 2 e– Sn(s) -0.14 Pb2+(aq) + 2 e– Pb(s) -0.13 2 H+(aq) + 2 e– H2(g) 0.00 SO42–(aq) + 4 H+(aq) + 2 e– H2SO3(aq) + H2O(l) +0.20 Cu2+(aq) + 2 e– Cu(s) +0.34 O2(g) + 2 H2O(l) + 4 e– 4 OH–(aq) +0.40 I2(s) + 2 e– 2 I–(aq) +0.54 Fe3+(aq) + e– Fe2+(aq) +0.77 Ag+(aq) + e– Ag(s) +0.80 NO3–(aq) + 4 H+(aq) + 3 e– NO(g) + 2 H2O +0.96 Br2(l) + 2 e– 2 Br–(aq) +1.09 Pt2+(aq) + 2 e– Pt(s) +1.19 O2(g) + 4 H+(aq) + 4 e– 2 H2O(l) +1.23 Cr2O72–(aq) + 14 H+(aq) + 6 e– 2 Cr3+(aq) + 7 H2O(l) +1.33 Cl2(l) + 2 e– 2 Cl–(aq) +1.36 Au3+(aq) + 3 e– Au(s) +1.50 MnO4–(aq) + 8 H+(aq) + 5 e– Mn2+(aq) + 4 H2O(l) +1.51 PbO2(s) + 4 H+(aq) + SO42–(aq) + 2 e– PbSO4(s) + 2 H2O(l) +1.69 F2(l) + 2 e– 2 F–(aq)

+2.87

V KCI A B

Explanation / Answer

a)
At cathode reduction occurs
SInce Eo is more for Zn2+, its reduction will occur

Zn2+ + 2e- ---> Zn

b)
at anode oxidation occurs:
Mg ---> Mg2+ + 2e-

c)
Zn2+ + Mg ---> Zn + Mg2+

d)
Eocell = Eo cathode - Eo anode
= -0.76 V - (-2.36 V)
= 1.60 V
Answer: 1.60 V

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