1
MCQ (Single Correct Answer)

AIPMT 2014

(I)   H2O2 + O3 $$ \to $$ H2O + 2O2
(II)   H2O2 + Ag2O $$ \to $$ 2Ag + H2O + O2
Role of Hydrogen peroxide in the above reactions is respectvely
A
oxidizing in (I) and reducing in (II)
B
reducing in (I) and oxidizing (II)
C
reducing in (I) and (II)
D
oxidizing in (I) and (II)

Explanation



So, H2O2 acts as reducing agent in all those reactions in which O2 is evolved.
2
MCQ (Single Correct Answer)

AIPMT 2014

The pair of compounds that can exist together is
A
FeCl3, SnCl2
B
HgCl2, SnCl2
C
FeCl2, SnCl2
D
FeCl3, KI

Explanation

Both FeCl2 and SnCl2 are reducing agents with low oxidation numbers.
3
MCQ (Single Correct Answer)

AIPMT 2012 Prelims

A mixture of potassium chlorate, oxalic acid and sulphuric acid is heated. During the reaction which element undergoes maximum change in the oxidation number?
A
S
B
H
C
Cl
D
C

Explanation

KClO3 + C2H2O4 + H2SO4 $$ \to $$ K2SO4 + CO2 + KCl + H2O

Maximum change in oxidation number of chlorine, i.e., from +5 to –1.
4
MCQ (Single Correct Answer)

AIPMT 2012 Prelims

When Cl2 gas reacts with hot and concentrated sodium hydroxide solution, the oxidation number of chlorine changes from
A
zero to +1 and zero to $$-$$5
B
zero to $$-$$1 and zero to +5
C
zero to $$-$$1 and zero to +3
D
zero to +1 and zero to $$-$$3

Explanation



This is an example of disproportionation reaction and oxidation state of chlorine changes from 0 to –1 and +5.

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