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Redox Reactions

Multiple Choice Questions

21.

In the disproportionation reaction,

3HClO₃ → HClO₄+ Cl₂+ 2O₂+ H₂O

the equivalent mass of the oxidising agent is (molar mass of HClO₃ = 84.45)

16.89
32.22
84.45
28.15

22.

A compound in which a metal ion M^x+ (Z = 25) has a spin only magnetic moment of $\sqrt{24}$ BM. The number of unpaired electrons in the compound and the oxidation state of the metal ion are respectively

4 and 2
5 and 3
3 and 2
4 and 3

23.

To an aqueous solution containing anions a few drops of acidified KMnO₄ are added. Which one of the following anions, if present will not decolourise the KMnO₄ solution ?

I^-
CO $_{3}^{2 -}$
S^2-
NO $_{2}^{-}$

24.

In the following reaction,

M^x+ + MnO $_{4}^{-}$ → MO $_{3}^{-}$ + Mn²⁺ + $\frac{1}{2}$ O₂

If one mole of MnO $_{4}^{-}$ oxidises 2.5 moles of M^x+, then the value of x is

25.
MnO^-₄ ions are reduced in acidic condition to Mn²⁺ ions whereas they are reduced in neutral condition to MnO₂. The oxidation of 25 mL of a solution X containing Fe²⁺ ions required in acidic condition 20 mL of a solution Y containing MnO^-₄ ions. What volume of solution Y would be required to oxidise 25 mL of a solution X containing Fe²⁺ ions in neutral condition?

11.4 mL

12.0 mL

33.3 mL

35.0 mL

33.3 mL

$In acidic medium, {MnO}_{4}^{-} is reduced to {Mn}^{2 +} \overset{+ 7}{Mn} O_{4}^{-} \to {Mn}^{2 +} Change in oxidation number = 7 - 2 = 5 Solution X Solution Y N_{1} V_{1} = N_{2} V_{2} For {Fe}^{2 +} For {MnO}_{4}^{-} N x 25 = 5 M x V [∴ For {MnO}_{4}^{-}, N = 5 M in acidic medium] 25 N = 5 M x 20 25 N = 100 M . . . . . (i) In neutral medium, {MnO}_{4}^{-} is reduce to {MnO}_{2} \overset{+ 7}{Mn} O_{4}^{-} \to \overset{+ 4}{Mn} O_{2} Change in oxidation number = 7 - 4 = 3 Solution X Solution Y N_{1} V_{1} = N_{2} V_{2} For {Fe}^{2 +} For {MnO}_{4}^{-} 25 x N = 3 M x V [∴ For {MnO}_{4}^{-} N = 3 M in neutral medium] 25 N = 3 M x V . . . . . (ii) From Eqs (i) and (ii) 100 M = 3 M \times V V = \frac{100}{3} = 33.3 mL$