6) Electrolysis of molten KCl produces molecular chlorine at the anode; however,

Question

6) Electrolysis of molten KCl produces molecular chlorine at the anode; however, in the electrolysis of an aqueous KCl solution, a gas is evolved. What is the gas and why is it produced? Explain.
7) The electrolytic refining of copper involves the oxidaton of impure copper containing such metals as iron and nickel (oxidized to copper(II), iron(II), and nickel(II) ions) at the anode and then reduction of the copper(II) ion to copper metal at the cathode. Explain why the iron(II) and nickel(II) ions are not deposited on the cathode. than the actual mass of copper oxidilptu. solution, a gas is evolved. What is the gas and why is it produced? Explain. (oxidized to copper(II), iron(II), and nickel(lI) ions) at the anode and then reduction of the copper(lI) ion to copper 6, Electrolysis of molten KCI produces molecular chlorine at the anode; however, in the electrolysis of an aqueous KCI 7. The electrolytic refining of copper involves the oxidaton of impure copper containing such metals as iron and nickel metal at the cathode. Explain why the iron(II) and nickel(II) ions are not deposited on the cathode

Explanation / Answer

6) When molten KCl is electrolyzed the dissociation taking place is as following

            KCl (aq) = K+ (aq) + Cl- (aq)

The K+ ion goes to the cathode and the Cl- ion goes to the anode.

When an aqueous solution of KCl is electrolyzed along with KCl water is also dissociated.

           H2O = H+ (aq) + OH- (aq)

So, at anode there is scope of formation of Oxygen gas from the hydroxide anions.

          4 OH = 2 H2O + O2 (g)

7) Let us take a look at the reduction potentials of these ions.

          Cu2+ (aq) + 2 e- = Cu (s)     E0 = +0.34 V

          Fe2+ (aq) + 2 e- = Fe (s)     E0 = -0.44 V

          Ni2+ (aq) + 2 e- = Ni (s)     E0 = -0.25 V

As the reduction of Ni(II) and Fe(II) are not so spontaneous like that of Cu(II) they are not deposited in the cathode.

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