Answer:
The standard reaction free energy = -144 kj
Explanation:
According to Electrochemical series
Standard reduction potential of
- Cl₂ + 2 e⁻ → 2 Cl⁻ E⁰ = +1.36 volt .................(i)
- MnO₄⁻ + 8H⁺ + 5 e⁻ → Mn²⁺ + 4 H₂O E⁰ = +1.51 volt ..................(ii)
Since Permanganate have more positive reduction potential so it is used as a cathode half cell and chlorine as a anode half cell
Cathode half cell (Reduction) MnO₄⁻ + 8H⁺ + 5 e⁻ → Mn²⁺ + 4 H₂O ...(3)
Anode half cell (Oxidation) 2 Cl⁻ → Cl₂ + 2 e⁻ ...............................(4)
Multiplication by 2 of equation (3) and by 5 of equation(4)
10Cl⁻(aq) + 2MnO₄⁻(aq) + 16H⁺(aq) = 5Cl₂(g) + 2Mn²⁺(aq) + 8H₂O(l)
E.M.F of the combined cell reaction
E⁰ = E⁰cathode - E⁰anode = 1.51 - 1.36 = 0.15 v
⇒ ΔG⁰ reaction = - nF E⁰cell
n = no, of electron exchange = 10
⇒ΔG⁰ reaction = - 10 x 96500 x 0.15
= - 144750 j
= - 144 kj (round off by 3 significant fig.)