The Edison storage cells is represented as
Fe(s) | FeO(s) | KOH (aq) | Ni₂O₃(s) | Ni(s)
The half-cell reactions are:
Ni₂O₃ + H₂O (l) + 2e^- $$\leftrightharpoons$$ 2NiO(s) + 2OH^-; E^o = +0.40V
FeO(s) + H₂O(l) + 2e^- $$\leftrightharpoons$$ Fe(s) + 2OH^-; E^o = -0.87V
(i) What is the cell reaction?
(ii) What is the cell e.m.f? How does it depend on the concentration of KOH?
(iii) What is the maximum amount of electrical energy that can be obtained from one mole of Ni₂O₃?

The standard reduction potential for the half-cell
$$NO_3^-$$ + 2H⁺ (aq) + e $$\to$$ NO₂ (g) + H₂O is 0.78 V
(i) Calculate the reduction potential in 8 M H⁺
(ii) What will be the reduction potential of the half-cell in a neutral solution? Assume all the other species to be at unit concentration.

Chromium metal can be plated out from an acidic solution containing CrO₃ according to the following equation
CrO₃ (aq) + 6H⁺ (aq) + 6e^- $$\to$$ Cr(s) + 3H₂O
Calculate (i) how many grams of chromium will be plated out by 24,000 coulombs and (ii) how long will it take to plate out 1.5 g of chromium by using 12.5 amp current.

An aqueous solution of NaCl on electrolysis gives H₂(g), Cl₂(g) and NaOH according to the reaction:
2Cl^- (aq) + 2H₂O = 2OH^- (aq) + H₂ (g) + Cl₂ (g)
A direct current of 25 amperes with a current efficiency of 62 % is passed through 20 litres of NaCl solution (20% by weight). Write down the reactions taking place at the anode and cathode. How long will it take to produce 1kg of Cl₂? What will be the molarity of the solution with respect to hydroxide ion? (Assume no loss due to evaporation)