Auto Oxidation and Disproportionation MCQs

The term “oxidation” refers to any chemical change involving an increase in oxidation number, while “reduction” refers to a change resulting in a decrease in oxidation number. Therefore, oxidation involves the loss of electrons, and reduction involves the gain of electrons. An oxidizing agent is a substance containing an atom that shows a decrease in oxidation number, whereas a reducing agent is a substance containing an atom that shows an increase in oxidation number. Oxidation and reduction always occur together and must balance each other. The terms “oxidizing agent” and “reducing agent” apply to the entire substance, not just a single atom. If a reagent acts as both an oxidizing and reducing agent, it undergoes autoxidation or disproportionation.

Disproportionation means

(a) only oxidation
(b) only reduction
(c) both, oxidation and reduction of a reactant
(d) neither oxidation nor reduction

The compounds behaving both as oxidizing, as well as a reducing agent, is

(a) H2O2
(b) SO2
(c) HNO2
(d) All

Which one of the following will not reduce an acidified solution of potassium dichromate (VI)?

(a) (CH3)2C(OH)CH3
(b) FeSO4
(c) CH3CH2CH(OH)CH3
(d) Zn

The decomposition of KClO3 to KCl and O2 on heating is an example of

(a) intermolecular redox change
(b) intramolecular redox change
(c) disproportionation or auto redox change
(d) none of these

Which of the following has been arranged in order of decreasing average oxidation number of sulphur?

(a) H2S2O7 > Na2S4O6 > Na2S2O3 > S8
(b) SO2+ > SO42- > SO32- > HSO4–
(c) H2SO5 > H2SO3 > SCl2 > H2S
(d) H2SO4 > SO2 > H2S > H2S2O8

A substance which can be oxidised as well as reduced easily is

(a) HCl
(b) HClO
(c) HClO3
(d) B and C

25.4g of iodine and 14.2g of chlorine is made to react completely to yield a mixture of ICl and ICl3. Calculate the ratio of moles of ICl and ICl3

(a) 1:1
(b) 1:2
(c) 1:3
(d) 2:3

Oxidation numbers of chlorine in Cl2O, Cl2 and ClO3– are respectively

(a) +1, -1, +5
(b) +1, 0, -1
(c) -1, 0, +1
(d) +1, 0, +5

The oxidation number of iron in Fe3O4 is

(a) +2
(b) +3
(c) 8/3
(d) A and B

Equivalent mass of oxidising agent in the reaction

SO2 + 2H2S → 3S + 2H2O

(a) 32
(b) 64
(c) 16
(d) 8