Question

Ceric ammonium sulphate and potassium permanganate are used as oxidising agents in acidic medium for oxidation of ferrous ammonium sulphate to ferric sulphate. The ratio, of number of moles of ceric ammonium sulphate required per mole of ferrous ammonium sulphate to the number of moles of ferrous ammonium sulphate to the number of moles of $KMn{O}_4$ required per mole of ferrous ammonium sulphate is:

• A. $5.0$
• B. $0.2$
• C. $0.6$
• D. $2.0$

Answer 1

Answer: (A)

$5.0$

$2KMn{O}_4+8H_{2}S{O}_4+10FeS{O}_4\cdot {\left({NH}_4\right)}_{2}S{O}_4\cdot 6H_{2}O⟶K_{2}S{O}_4+2MnS{O}_4+5{Fe}_2{\left(S{O}_4\right)}_3+10{\left({NH}_4\right)}_{2}S{O}_4+68H_{2}O$

consumption of $KMn{O}_4$ per mole of

$FeS{O}_4\cdot {\left({NH}_4\right)}_{2}S{O}_4$ is $1/5$ mole

${Fe}^{2+}+{Ce}^{4+}⟶{Fe}^{3+}+{Ce}^{3+}$

So, ratio $=\frac{\text{moles of ceric ammonium sulphate}}{\text{moles of potassium permangnate}}=\frac{1}{1/5}=5.0$
Option A is correct.