NEW
New Website Launch
Experience the best way to solve previous year questions with mock tests (very detailed analysis), bookmark your favourite questions, practice etc...
1

NEET 2020 Phase 1

MCQ (Single Correct Answer)
What is the change in oxidation number of carbon in the following reaction?
CH4(g) + 4Cl2(g) $$ \to $$ CCl4(l) + 4HCl(g)
A
0 to + 4
B
$$ - $$4 to + 4
C
0 to $$ - $$ 4
D
+ 4 to + 4

Explanation


Change in oxidation state of carbon is from $$ - $$ 4 to + 4
2

NEET 2019

MCQ (Single Correct Answer)
Which of the following reactions are disproportionation reaction?

(a) 2Cu+ $$ \to $$ Cu2+ + Cu0
(b) 3MnO42+ + 4H+ $$ \to $$ 2MnO4- + MnO2 + 2H2O
(c) 2KMnO4 $$\buildrel \Delta \over \longrightarrow $$ K2MnO4 + MnO2 + O2
(d) 2MnO4- + 3Mn2+ + 2H2O $$ \to $$ 5MnO2 + 4$${H^ \oplus }$$

Select the correct option from the following :
A
(a), (c) and (d)
B
(a) and (b) only
C
(a) and (d) only
D
(a), (b) and (c)

Explanation

In a disproportionation reaction, same substance undergoes oxidation (increase in oxidation number) and reduction (decrease in oxidation number forming two different products.
3

NEET 2018

MCQ (Single Correct Answer)
The correct order of N-compounds in its decreasing order of oxidation states is
A
HNO3 , NO, N2 , NH4Cl
B
HNO3 , NO, NH4Cl, N2
C
HNO3 , NH4Cl, NO, N
D
NH4Cl, N2 , NO, HNO3

Explanation

$$H\mathop N\limits^{ + 5} {O_3},\mathop N\limits^{ + 2} O,\mathop {{N_2}}\limits^0 ,\mathop N\limits^{ - 3} {H_4}Cl$$
4

NEET 2018

MCQ (Single Correct Answer)
Consider the change in oxidation state of bromine corresponding to different emf values as shown in the given diagram :
Then the species undergoing disproportionation is :
A
BrO4
B
BrO3
C
Br2
D
HBrO

Explanation

Calculate Eocell corresponding to each compound undergoing disproportionation reaction. The reaction for which Eocell comes out + ve is spontaneous.

HBrO $$ \to $$ Br2, EoHBrO/Br2 = 1.595 V

HBrO $$ \to $$ BrO3, EoBrO3-/HBrO = 1.595 V

Eocell for the disproportionation of HBrO,

Eocell = EoHBrO/Br2 - EoBrO3-/HBrO

= 1.595 - 1.5

= 0.095 V = + ve

So, Eocell > 0

So, $$\Delta $$Go < 0 (Spontaneous)

Joint Entrance Examination

JEE Main JEE Advanced WB JEE

Graduate Aptitude Test in Engineering

GATE CSE GATE ECE GATE EE GATE ME GATE CE GATE PI GATE IN

Medical

NEET

CBSE

Class 12