1
MCQ (Single Correct Answer)

NEET 2016 Phase 2

Hot concentrated sulphate acid is a moderately strong oxidizing agent. Which of the following reactions does not show oxidizing behaviour?
A
Cu + 2H2SO4 $$ \to $$ CuSO4 + SO2 + 2H2O
B
S + 2H2SO4 $$ \to $$ 3SO2 + 2H2O
C
C + 2H2SO4 $$ \to $$ CO2 + 2SO2 + 2H2O
D
CaF2 + H2SO4 $$ \to $$ CaSO4 + 2HF

Explanation

CaF2 + H2SO4 $$ \to $$ CaSO4 + 2HF

Here, the oxidation state of every atom remains the same so, it is not a redox reaction.
2
MCQ (Single Correct Answer)

AIPMT 2014

In acidic medium, H2O2 changes Cr2O72- to CrO5 which has two

($$-$$O$$-$$O$$-$$) bonds. Oxidation state of Cr in CrO5 is
A
+5
B
+3
C
+6
D
$$-$$10

Explanation

CrO5 has butterfly structure having two peroxo bonds.



Peroxo oxygen has –1 oxidation state.

Let oxidation state of Cr be ‘x’

CrO5 : x + 4(–1) + 1 (–2) = 0

$$ \Rightarrow $$ x = +6
3
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.
4
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.

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