Redox Reaction: JEE Mains Previous Year Questions (2020 - 2021) | Chemistry for JEE Main & Advanced PDF Download

 Page 1


2024 
 
Q1 - 2024 (01 Feb Shift 1) 
In acidic medium, K
2
Cr
2
O
7
 shows oxidising action as represented in the half reaction 
Cr
2
O
7
2 -
+ XH
+
+ Ye
-
? 2A + ZH
2
O 
X, Y, Z and A are respectively are: 
(1) 8,6,4 and Cr
2
O
3
 
(2) 14,7,6 and Cr
3+
 
(3) 8,4,6 and Cr
2
O
3
 
(4) 14,6,7and Cr
3+
 
Q2 - 2024 (01 Feb Shift 1) 
Which of the following reactions are disproportionation reactions? 
(A) Cu
+
? Cu
2+
+ Cu 
(B) 3MnO
4
2 -
+ 4H
+
? 2MnO
4
-
+ MnO
2
+ 2H
2
O 
(C) 2KMnO
4
? K
2
MnO
4
+ MnO
2
+ O
2
 
(D) 2MnO
4
-
+ 3Mn
2+
+ 2H
2
O ? 5MnO
2
+ 4H
+
 
Choose the correct answer from the options given below: 
(1) (A), (B) 
(2) (B), (C), (D) 
(3) (A), (B), (C) 
(4) (A), (D) 
Q3 - 2024 (01 Feb Shift 1) 
Given below are two statements : 
Statement (I): Potassium hydrogen phthalate is a primary standard for standardisation of 
sodium hydroxide solution. 
Statement (II): In this titration phenolphthalein can be used as indicator. 
In the light of the above statements, choose the most appropriate answer from the 
options given below: 
(1) Both Statement I and Statement II are correct 
(2) Statement I is correct but Statement II is incorrect 
(3) Statement I is incorrect but Statement II is correct 
(4) Both Statement I and Statement II are incorrect 
Q4 - 2024 (27 Jan Shift 2) 
Which of the following cannot function as an oxidising agent? 
(1) N
3 -
 
(2) SO
4
2 -
 
Page 2


2024 
 
Q1 - 2024 (01 Feb Shift 1) 
In acidic medium, K
2
Cr
2
O
7
 shows oxidising action as represented in the half reaction 
Cr
2
O
7
2 -
+ XH
+
+ Ye
-
? 2A + ZH
2
O 
X, Y, Z and A are respectively are: 
(1) 8,6,4 and Cr
2
O
3
 
(2) 14,7,6 and Cr
3+
 
(3) 8,4,6 and Cr
2
O
3
 
(4) 14,6,7and Cr
3+
 
Q2 - 2024 (01 Feb Shift 1) 
Which of the following reactions are disproportionation reactions? 
(A) Cu
+
? Cu
2+
+ Cu 
(B) 3MnO
4
2 -
+ 4H
+
? 2MnO
4
-
+ MnO
2
+ 2H
2
O 
(C) 2KMnO
4
? K
2
MnO
4
+ MnO
2
+ O
2
 
(D) 2MnO
4
-
+ 3Mn
2+
+ 2H
2
O ? 5MnO
2
+ 4H
+
 
Choose the correct answer from the options given below: 
(1) (A), (B) 
(2) (B), (C), (D) 
(3) (A), (B), (C) 
(4) (A), (D) 
Q3 - 2024 (01 Feb Shift 1) 
Given below are two statements : 
Statement (I): Potassium hydrogen phthalate is a primary standard for standardisation of 
sodium hydroxide solution. 
Statement (II): In this titration phenolphthalein can be used as indicator. 
In the light of the above statements, choose the most appropriate answer from the 
options given below: 
(1) Both Statement I and Statement II are correct 
(2) Statement I is correct but Statement II is incorrect 
(3) Statement I is incorrect but Statement II is correct 
(4) Both Statement I and Statement II are incorrect 
Q4 - 2024 (27 Jan Shift 2) 
Which of the following cannot function as an oxidising agent? 
(1) N
3 -
 
(2) SO
4
2 -
 
(3) BrO
3
-
 
(4) MnO
4
-
 
Q5 - 2024 (29 Jan Shift 1) 
KMnO
4
decomposes on heating at 513K to form O
2
 along with 
(1) MnO
2
&K
2
O
2
 
(2) K
2
MnO
4
& ?? ?? 
(3) Mn&KO
2
 
(4) K
2
MnO
4
&MnO
2
 
Q6 - 2024 (29 Jan Shift 1) 
Chlorine undergoes disproportionation in alkaline medium as shown below : 
aCl
2
(g) + bOH
-
(aq) ? cClO
-
(aq) + dCl
-
(aq) + e
2
O( ?? ) 
The values of ?? , ?? , ?? and ?? in a balanced redox reaction are respectively: 
(1) 1, 2, 1 and 1 
(2) 2, 2, 1 and 3 
(3) 3, 4, 4 and 2 
(4) 2, 4, 1 and 3 
Q7 - 2024 (29 Jan Shift 2) 
If 50mL of 0.5M oxalic acid is required to neutralise 25mL of NaOH solution, the amount 
of NaOH in 50mL of given NaOH solution is g. 
Q8 - 2024 (30 Jan Shift 1) 
2MnO
4
-
+ bI
-
+ cH
2
O ? xI
2
+ yMnO
2
+ zOH
-
 
If the above equation is balanced with integer coefficients, the value of ?? is 
Q9 - 2024 (30 Jan Shift 2) 
Total number of species from the following which can undergo disproportionation 
reaction 
H
2
O
2
, ClO
3
-
, P
4
, Cl
2
, Ag, Cu
+1
, F
2
, NO
2
, K
+
 
Q10 - 2024 (31 Jan Shift 2) 
Given below are two statements : 
Statement I: S
8
 solid undergoes disproportionation reaction under alkalineconditions to 
form S
2 -
 and S
2
O
3
2 -
 
Statement II: ClO
4
-
can undergodisproportionation reaction under acidic condition. 
In the light of the above statements, choose the most appropriate answer from the 
options givenbelow : 
(1) Statement I is correct but statement II is incorrect. 
(2) Statement I is incorrect but statement II is correct 
Page 3


2024 
 
Q1 - 2024 (01 Feb Shift 1) 
In acidic medium, K
2
Cr
2
O
7
 shows oxidising action as represented in the half reaction 
Cr
2
O
7
2 -
+ XH
+
+ Ye
-
? 2A + ZH
2
O 
X, Y, Z and A are respectively are: 
(1) 8,6,4 and Cr
2
O
3
 
(2) 14,7,6 and Cr
3+
 
(3) 8,4,6 and Cr
2
O
3
 
(4) 14,6,7and Cr
3+
 
Q2 - 2024 (01 Feb Shift 1) 
Which of the following reactions are disproportionation reactions? 
(A) Cu
+
? Cu
2+
+ Cu 
(B) 3MnO
4
2 -
+ 4H
+
? 2MnO
4
-
+ MnO
2
+ 2H
2
O 
(C) 2KMnO
4
? K
2
MnO
4
+ MnO
2
+ O
2
 
(D) 2MnO
4
-
+ 3Mn
2+
+ 2H
2
O ? 5MnO
2
+ 4H
+
 
Choose the correct answer from the options given below: 
(1) (A), (B) 
(2) (B), (C), (D) 
(3) (A), (B), (C) 
(4) (A), (D) 
Q3 - 2024 (01 Feb Shift 1) 
Given below are two statements : 
Statement (I): Potassium hydrogen phthalate is a primary standard for standardisation of 
sodium hydroxide solution. 
Statement (II): In this titration phenolphthalein can be used as indicator. 
In the light of the above statements, choose the most appropriate answer from the 
options given below: 
(1) Both Statement I and Statement II are correct 
(2) Statement I is correct but Statement II is incorrect 
(3) Statement I is incorrect but Statement II is correct 
(4) Both Statement I and Statement II are incorrect 
Q4 - 2024 (27 Jan Shift 2) 
Which of the following cannot function as an oxidising agent? 
(1) N
3 -
 
(2) SO
4
2 -
 
(3) BrO
3
-
 
(4) MnO
4
-
 
Q5 - 2024 (29 Jan Shift 1) 
KMnO
4
decomposes on heating at 513K to form O
2
 along with 
(1) MnO
2
&K
2
O
2
 
(2) K
2
MnO
4
& ?? ?? 
(3) Mn&KO
2
 
(4) K
2
MnO
4
&MnO
2
 
Q6 - 2024 (29 Jan Shift 1) 
Chlorine undergoes disproportionation in alkaline medium as shown below : 
aCl
2
(g) + bOH
-
(aq) ? cClO
-
(aq) + dCl
-
(aq) + e
2
O( ?? ) 
The values of ?? , ?? , ?? and ?? in a balanced redox reaction are respectively: 
(1) 1, 2, 1 and 1 
(2) 2, 2, 1 and 3 
(3) 3, 4, 4 and 2 
(4) 2, 4, 1 and 3 
Q7 - 2024 (29 Jan Shift 2) 
If 50mL of 0.5M oxalic acid is required to neutralise 25mL of NaOH solution, the amount 
of NaOH in 50mL of given NaOH solution is g. 
Q8 - 2024 (30 Jan Shift 1) 
2MnO
4
-
+ bI
-
+ cH
2
O ? xI
2
+ yMnO
2
+ zOH
-
 
If the above equation is balanced with integer coefficients, the value of ?? is 
Q9 - 2024 (30 Jan Shift 2) 
Total number of species from the following which can undergo disproportionation 
reaction 
H
2
O
2
, ClO
3
-
, P
4
, Cl
2
, Ag, Cu
+1
, F
2
, NO
2
, K
+
 
Q10 - 2024 (31 Jan Shift 2) 
Given below are two statements : 
Statement I: S
8
 solid undergoes disproportionation reaction under alkalineconditions to 
form S
2 -
 and S
2
O
3
2 -
 
Statement II: ClO
4
-
can undergodisproportionation reaction under acidic condition. 
In the light of the above statements, choose the most appropriate answer from the 
options givenbelow : 
(1) Statement I is correct but statement II is incorrect. 
(2) Statement I is incorrect but statement II is correct 
(3) Both statement I and statement II are incorrect 
(4) Both statement I and statement II are correct 
Answer Key 
Q1 (4)  
Q2 (1)  
Q3 (1)  
Q4 (1)  
Q5 (4)  
Q6 (1)  
Q7 (4)  
Q8 (8)  
Q9 (6)  
Q10 (1)  
 
Solutions 
Q1. 
The balanced reaction is, 
Cr
2
O
7
2 -
+ 14H
+
+ 6e
-
? 2Cr
3+
+ 7H
2
O 
X = 14 
Y = 6 
A = 7 
Q2. 
When a particular oxidation state becomes less stable relative to other oxidation state, 
one lower, one higher, it is said to undergo disproportionation. 
Cu
+
? Cu
2+
+ Cu 
3MnO
4
2 -
+ 4H
+
? 2MnO
4
-
+ MnO
2
+ 2H
2
O 
Q3. 
Page 4


2024 
 
Q1 - 2024 (01 Feb Shift 1) 
In acidic medium, K
2
Cr
2
O
7
 shows oxidising action as represented in the half reaction 
Cr
2
O
7
2 -
+ XH
+
+ Ye
-
? 2A + ZH
2
O 
X, Y, Z and A are respectively are: 
(1) 8,6,4 and Cr
2
O
3
 
(2) 14,7,6 and Cr
3+
 
(3) 8,4,6 and Cr
2
O
3
 
(4) 14,6,7and Cr
3+
 
Q2 - 2024 (01 Feb Shift 1) 
Which of the following reactions are disproportionation reactions? 
(A) Cu
+
? Cu
2+
+ Cu 
(B) 3MnO
4
2 -
+ 4H
+
? 2MnO
4
-
+ MnO
2
+ 2H
2
O 
(C) 2KMnO
4
? K
2
MnO
4
+ MnO
2
+ O
2
 
(D) 2MnO
4
-
+ 3Mn
2+
+ 2H
2
O ? 5MnO
2
+ 4H
+
 
Choose the correct answer from the options given below: 
(1) (A), (B) 
(2) (B), (C), (D) 
(3) (A), (B), (C) 
(4) (A), (D) 
Q3 - 2024 (01 Feb Shift 1) 
Given below are two statements : 
Statement (I): Potassium hydrogen phthalate is a primary standard for standardisation of 
sodium hydroxide solution. 
Statement (II): In this titration phenolphthalein can be used as indicator. 
In the light of the above statements, choose the most appropriate answer from the 
options given below: 
(1) Both Statement I and Statement II are correct 
(2) Statement I is correct but Statement II is incorrect 
(3) Statement I is incorrect but Statement II is correct 
(4) Both Statement I and Statement II are incorrect 
Q4 - 2024 (27 Jan Shift 2) 
Which of the following cannot function as an oxidising agent? 
(1) N
3 -
 
(2) SO
4
2 -
 
(3) BrO
3
-
 
(4) MnO
4
-
 
Q5 - 2024 (29 Jan Shift 1) 
KMnO
4
decomposes on heating at 513K to form O
2
 along with 
(1) MnO
2
&K
2
O
2
 
(2) K
2
MnO
4
& ?? ?? 
(3) Mn&KO
2
 
(4) K
2
MnO
4
&MnO
2
 
Q6 - 2024 (29 Jan Shift 1) 
Chlorine undergoes disproportionation in alkaline medium as shown below : 
aCl
2
(g) + bOH
-
(aq) ? cClO
-
(aq) + dCl
-
(aq) + e
2
O( ?? ) 
The values of ?? , ?? , ?? and ?? in a balanced redox reaction are respectively: 
(1) 1, 2, 1 and 1 
(2) 2, 2, 1 and 3 
(3) 3, 4, 4 and 2 
(4) 2, 4, 1 and 3 
Q7 - 2024 (29 Jan Shift 2) 
If 50mL of 0.5M oxalic acid is required to neutralise 25mL of NaOH solution, the amount 
of NaOH in 50mL of given NaOH solution is g. 
Q8 - 2024 (30 Jan Shift 1) 
2MnO
4
-
+ bI
-
+ cH
2
O ? xI
2
+ yMnO
2
+ zOH
-
 
If the above equation is balanced with integer coefficients, the value of ?? is 
Q9 - 2024 (30 Jan Shift 2) 
Total number of species from the following which can undergo disproportionation 
reaction 
H
2
O
2
, ClO
3
-
, P
4
, Cl
2
, Ag, Cu
+1
, F
2
, NO
2
, K
+
 
Q10 - 2024 (31 Jan Shift 2) 
Given below are two statements : 
Statement I: S
8
 solid undergoes disproportionation reaction under alkalineconditions to 
form S
2 -
 and S
2
O
3
2 -
 
Statement II: ClO
4
-
can undergodisproportionation reaction under acidic condition. 
In the light of the above statements, choose the most appropriate answer from the 
options givenbelow : 
(1) Statement I is correct but statement II is incorrect. 
(2) Statement I is incorrect but statement II is correct 
(3) Both statement I and statement II are incorrect 
(4) Both statement I and statement II are correct 
Answer Key 
Q1 (4)  
Q2 (1)  
Q3 (1)  
Q4 (1)  
Q5 (4)  
Q6 (1)  
Q7 (4)  
Q8 (8)  
Q9 (6)  
Q10 (1)  
 
Solutions 
Q1. 
The balanced reaction is, 
Cr
2
O
7
2 -
+ 14H
+
+ 6e
-
? 2Cr
3+
+ 7H
2
O 
X = 14 
Y = 6 
A = 7 
Q2. 
When a particular oxidation state becomes less stable relative to other oxidation state, 
one lower, one higher, it is said to undergo disproportionation. 
Cu
+
? Cu
2+
+ Cu 
3MnO
4
2 -
+ 4H
+
? 2MnO
4
-
+ MnO
2
+ 2H
2
O 
Q3. 
Statement (I) : Potassium hydrogen phthalate is a primary standard for standardisation 
of sodium hydroxide solution as it is economical and its concentration does not changes 
with time. 
Phenolphthalein can acts as indicator in acid base titration as it shows colour in pH 
range 8.3 to 10.1 
Q4. 
In N
3 -
 ion ' N ' is present in its lowest possible oxidation state, hence it cannot be 
reduced further because of which it cannot act as an oxidizing agent. 
Q5. 
KMnO
4
?
?
K
2
MnO
4
+ MnO
2
+ O
2
 
Q6. 
 
Q7. 
Equivalent of Oxalic acid = Equivalents of NaOH 
50 × 0.5 × 2 = 25 × M × 1 
M
NaOH
= 2M 
W
NaOH
in50ml = 2 × 50 × 40 × 10
-3
g = 4g 
Q8. 
 
Adding oxidation half and reduction half, net reaction is 
2MnO
4
-
+ 6I
-
+ 4H
2
O ? 3I
2
+ 2MnO
2
+ 8OH
-
 
Page 5


2024 
 
Q1 - 2024 (01 Feb Shift 1) 
In acidic medium, K
2
Cr
2
O
7
 shows oxidising action as represented in the half reaction 
Cr
2
O
7
2 -
+ XH
+
+ Ye
-
? 2A + ZH
2
O 
X, Y, Z and A are respectively are: 
(1) 8,6,4 and Cr
2
O
3
 
(2) 14,7,6 and Cr
3+
 
(3) 8,4,6 and Cr
2
O
3
 
(4) 14,6,7and Cr
3+
 
Q2 - 2024 (01 Feb Shift 1) 
Which of the following reactions are disproportionation reactions? 
(A) Cu
+
? Cu
2+
+ Cu 
(B) 3MnO
4
2 -
+ 4H
+
? 2MnO
4
-
+ MnO
2
+ 2H
2
O 
(C) 2KMnO
4
? K
2
MnO
4
+ MnO
2
+ O
2
 
(D) 2MnO
4
-
+ 3Mn
2+
+ 2H
2
O ? 5MnO
2
+ 4H
+
 
Choose the correct answer from the options given below: 
(1) (A), (B) 
(2) (B), (C), (D) 
(3) (A), (B), (C) 
(4) (A), (D) 
Q3 - 2024 (01 Feb Shift 1) 
Given below are two statements : 
Statement (I): Potassium hydrogen phthalate is a primary standard for standardisation of 
sodium hydroxide solution. 
Statement (II): In this titration phenolphthalein can be used as indicator. 
In the light of the above statements, choose the most appropriate answer from the 
options given below: 
(1) Both Statement I and Statement II are correct 
(2) Statement I is correct but Statement II is incorrect 
(3) Statement I is incorrect but Statement II is correct 
(4) Both Statement I and Statement II are incorrect 
Q4 - 2024 (27 Jan Shift 2) 
Which of the following cannot function as an oxidising agent? 
(1) N
3 -
 
(2) SO
4
2 -
 
(3) BrO
3
-
 
(4) MnO
4
-
 
Q5 - 2024 (29 Jan Shift 1) 
KMnO
4
decomposes on heating at 513K to form O
2
 along with 
(1) MnO
2
&K
2
O
2
 
(2) K
2
MnO
4
& ?? ?? 
(3) Mn&KO
2
 
(4) K
2
MnO
4
&MnO
2
 
Q6 - 2024 (29 Jan Shift 1) 
Chlorine undergoes disproportionation in alkaline medium as shown below : 
aCl
2
(g) + bOH
-
(aq) ? cClO
-
(aq) + dCl
-
(aq) + e
2
O( ?? ) 
The values of ?? , ?? , ?? and ?? in a balanced redox reaction are respectively: 
(1) 1, 2, 1 and 1 
(2) 2, 2, 1 and 3 
(3) 3, 4, 4 and 2 
(4) 2, 4, 1 and 3 
Q7 - 2024 (29 Jan Shift 2) 
If 50mL of 0.5M oxalic acid is required to neutralise 25mL of NaOH solution, the amount 
of NaOH in 50mL of given NaOH solution is g. 
Q8 - 2024 (30 Jan Shift 1) 
2MnO
4
-
+ bI
-
+ cH
2
O ? xI
2
+ yMnO
2
+ zOH
-
 
If the above equation is balanced with integer coefficients, the value of ?? is 
Q9 - 2024 (30 Jan Shift 2) 
Total number of species from the following which can undergo disproportionation 
reaction 
H
2
O
2
, ClO
3
-
, P
4
, Cl
2
, Ag, Cu
+1
, F
2
, NO
2
, K
+
 
Q10 - 2024 (31 Jan Shift 2) 
Given below are two statements : 
Statement I: S
8
 solid undergoes disproportionation reaction under alkalineconditions to 
form S
2 -
 and S
2
O
3
2 -
 
Statement II: ClO
4
-
can undergodisproportionation reaction under acidic condition. 
In the light of the above statements, choose the most appropriate answer from the 
options givenbelow : 
(1) Statement I is correct but statement II is incorrect. 
(2) Statement I is incorrect but statement II is correct 
(3) Both statement I and statement II are incorrect 
(4) Both statement I and statement II are correct 
Answer Key 
Q1 (4)  
Q2 (1)  
Q3 (1)  
Q4 (1)  
Q5 (4)  
Q6 (1)  
Q7 (4)  
Q8 (8)  
Q9 (6)  
Q10 (1)  
 
Solutions 
Q1. 
The balanced reaction is, 
Cr
2
O
7
2 -
+ 14H
+
+ 6e
-
? 2Cr
3+
+ 7H
2
O 
X = 14 
Y = 6 
A = 7 
Q2. 
When a particular oxidation state becomes less stable relative to other oxidation state, 
one lower, one higher, it is said to undergo disproportionation. 
Cu
+
? Cu
2+
+ Cu 
3MnO
4
2 -
+ 4H
+
? 2MnO
4
-
+ MnO
2
+ 2H
2
O 
Q3. 
Statement (I) : Potassium hydrogen phthalate is a primary standard for standardisation 
of sodium hydroxide solution as it is economical and its concentration does not changes 
with time. 
Phenolphthalein can acts as indicator in acid base titration as it shows colour in pH 
range 8.3 to 10.1 
Q4. 
In N
3 -
 ion ' N ' is present in its lowest possible oxidation state, hence it cannot be 
reduced further because of which it cannot act as an oxidizing agent. 
Q5. 
KMnO
4
?
?
K
2
MnO
4
+ MnO
2
+ O
2
 
Q6. 
 
Q7. 
Equivalent of Oxalic acid = Equivalents of NaOH 
50 × 0.5 × 2 = 25 × M × 1 
M
NaOH
= 2M 
W
NaOH
in50ml = 2 × 50 × 40 × 10
-3
g = 4g 
Q8. 
 
Adding oxidation half and reduction half, net reaction is 
2MnO
4
-
+ 6I
-
+ 4H
2
O ? 3I
2
+ 2MnO
2
+ 8OH
-
 
( ? ?? = 8 
? Ans 8 
Q9. 
Intermediate oxidation state of element can undergo disproportionation. 
H
2
O
2
, ClO
3
-
, P
4
, Cl
2
, Cu
+1
, NO
2
 
Q10. 
S
1
: S
8
+ 12OH
?
? 4S
2 -
+ 2S
2
O
3
2 -
+ 6H
2
O 
S
2
: ClO
4
?
cannot undergo disproportionation reaction as chlorine is present in it's highest 
oxidation state.