JEE Main 2021 Answer Key Chemistry - Morning Shift (25-02-2021) Notes | EduRev

Mock Test Series for JEE Main & Advanced 2021

JEE : JEE Main 2021 Answer Key Chemistry - Morning Shift (25-02-2021) Notes | EduRev

 Page 1


JEE (MAIN)-2021 : Phase-1(25-02-2021)-M
PART–B : CHEMISTRY
SECTION - I
Multiple Choice Questions: This section contains 20
multiple choice questions. Each question has 4
choices (1), (2), (3) and (4), out of which ONLY ONE
is correct.
Choose the correct answer :
1. Which one of the following reactions will not
form acetaldehyde?
(1)
-
??????? ?
32 4
CrO H SO
32
CH CH OH
(2)
= + ?????? ?
2
Pd(II)/Cu(II)
22 2
HO
CH CH O
(3) ? ??? ?
Cu
32
573 K
CH CH OH
(4)
?????? ?
2
(i) DIBAL-H
3
(ii) H O
CH CN
Answer (1)
Sol.
32 4
CrO H SO
32 3
Jones reagent
CH CH OH CH COOH
-
????????
In the rest of the options acetaldehyde will be
formed.
2. Given below are two statements:
Statement-I: CeO
2
 can be used for oxidation of
aldehyde and ketones.
Statement-II: Aqueous solution of EuSO
4
 is a
strong reducing agent.
In the light of the above statements, choose
the correct answer from the options given
below:
(1) Both Statement I and Statement II are false
(2) Both Statement I and Statement II are true
(3) Statement I is true but Statement II is false
(4) Statement I is false but Statement II is true
Answer (2)
Sol. Ce and Eu have stable oxidation state of +3.
So 
4
2
CeO
?
 acts as oxidizing agent to get
reduced to +3 and 
2
4
EuSO
?
 acts as reducing
agent to get oxidized to +3.
3. Given below are two statements:
Statement-I : An allotrope of oxygen is an
important intermediate in the formation of
reducing smog.
Statement-II: Gases such as oxides of nitrogen
and sulphur present in troposphere contribute
to the fomation of photochemical smog.
In the light of the above statements, choose
the correct answer from the options given
below:
(1) Statement I is true but Statement II is false
(2) Both Statement I and Statement II are false
(3) Statement I is false but Statement II is true
(4) Both Statement I and Statement II are true
Answer (2)
Sol.  Reducing smog is a mixture of smoke, fog
and sulphur dioxide. It does not involve O
3
(allotrope of oxygen) during its formation.
 The main component of the photochemical
smog result from the action of sunlight on
unsaturated hydrocarbons and nitrogen
oxides. No involvement of oxides of S.
So the answer should be, both statements
false.
4. Which of the glycosidic linkage between
galactose and glucose is present in lactose?
(1) C-1 of galactose and C-4 of glucose
(2) C-1 of glucose and C-6 of galactose
(3) C-1 of galactose and C-6 of glucose
(4) C-1 of glucose and C-4 of galactose
Answer (1)
Sol.
OO
HH
OH OH
OH
OH OH
HH
O
HO H
H
CH OH
2
CH OH
2
HH
HH
22
11
33
5
5
6 6
44
?-D-Galactose ?-D-Glucose
Lactose
A glycosidic linkage is between C1 of
?-D- galactose and C4 of ?-D-glucose.
So option-1 is the correct answer.
Page 2


JEE (MAIN)-2021 : Phase-1(25-02-2021)-M
PART–B : CHEMISTRY
SECTION - I
Multiple Choice Questions: This section contains 20
multiple choice questions. Each question has 4
choices (1), (2), (3) and (4), out of which ONLY ONE
is correct.
Choose the correct answer :
1. Which one of the following reactions will not
form acetaldehyde?
(1)
-
??????? ?
32 4
CrO H SO
32
CH CH OH
(2)
= + ?????? ?
2
Pd(II)/Cu(II)
22 2
HO
CH CH O
(3) ? ??? ?
Cu
32
573 K
CH CH OH
(4)
?????? ?
2
(i) DIBAL-H
3
(ii) H O
CH CN
Answer (1)
Sol.
32 4
CrO H SO
32 3
Jones reagent
CH CH OH CH COOH
-
????????
In the rest of the options acetaldehyde will be
formed.
2. Given below are two statements:
Statement-I: CeO
2
 can be used for oxidation of
aldehyde and ketones.
Statement-II: Aqueous solution of EuSO
4
 is a
strong reducing agent.
In the light of the above statements, choose
the correct answer from the options given
below:
(1) Both Statement I and Statement II are false
(2) Both Statement I and Statement II are true
(3) Statement I is true but Statement II is false
(4) Statement I is false but Statement II is true
Answer (2)
Sol. Ce and Eu have stable oxidation state of +3.
So 
4
2
CeO
?
 acts as oxidizing agent to get
reduced to +3 and 
2
4
EuSO
?
 acts as reducing
agent to get oxidized to +3.
3. Given below are two statements:
Statement-I : An allotrope of oxygen is an
important intermediate in the formation of
reducing smog.
Statement-II: Gases such as oxides of nitrogen
and sulphur present in troposphere contribute
to the fomation of photochemical smog.
In the light of the above statements, choose
the correct answer from the options given
below:
(1) Statement I is true but Statement II is false
(2) Both Statement I and Statement II are false
(3) Statement I is false but Statement II is true
(4) Both Statement I and Statement II are true
Answer (2)
Sol.  Reducing smog is a mixture of smoke, fog
and sulphur dioxide. It does not involve O
3
(allotrope of oxygen) during its formation.
 The main component of the photochemical
smog result from the action of sunlight on
unsaturated hydrocarbons and nitrogen
oxides. No involvement of oxides of S.
So the answer should be, both statements
false.
4. Which of the glycosidic linkage between
galactose and glucose is present in lactose?
(1) C-1 of galactose and C-4 of glucose
(2) C-1 of glucose and C-6 of galactose
(3) C-1 of galactose and C-6 of glucose
(4) C-1 of glucose and C-4 of galactose
Answer (1)
Sol.
OO
HH
OH OH
OH
OH OH
HH
O
HO H
H
CH OH
2
CH OH
2
HH
HH
22
11
33
5
5
6 6
44
?-D-Galactose ?-D-Glucose
Lactose
A glycosidic linkage is between C1 of
?-D- galactose and C4 of ?-D-glucose.
So option-1 is the correct answer.
JEE (MAIN)-2021 : Phase-1(25-02-2021)-M
5. In which of the following pairs, the outer most
electronic configuration will be the same?
(1) Ni
2+ 
and Cu
+
(2) Fe
2+ 
and Co
+
(3) Cr
+ 
and Mn
2+
(4) V
2+ 
and Cr
+
Answer (3)
Sol.
Cr – 4 3d
+0 5
s
Mn s
2+ 0 5
 – 4 3d
have some electronic
configuration in the
outer most shell
6. The major product of the following chemical
reaction is:
3
2
42
1) H O ,
2)SOCl
32
3) Pd/BaSO ,H
CH CH CN ?
?
?
? ?????? ?
(1) CH
3
CH
2
CH
3
(2) CH
3
CH
2
CH
2
OH
(3) CH
3
CH
2
CHO
(4) (CH
3
CH
2
CO)
2
O
Answer (3)
Sol. CH
32
CH CN
HO
3
+
?
CH – CH – COOH
32
SOCl
2
CH – CH – C – Cl
32
O
O
CH – CH – C – H
32
Pd/BaSO , H
42
Correct option should be (3)
7. Identify A and B in the chemical reaction.
NO
2
OCH
3
?? ? ? ? ???? ?
HCl NaI
dryacetone
(major) major
[A] [B]
(1)
NO
2
OCH
3
Cl
A =
NO
2
OCH
3
I
B =
(2)
NO
2
OCH
3
Cl
A =
NO
2
OCH
3
Cl
B =
(3)
NO
2
OCH
3
Cl
A =
NO
2
I
Cl
B =
(4)
NO
2
OCH
3
Cl
A =
NO
2
I
Cl
B =
Answer (1)
Sol.
OCH
3
NO
2
HCl
+
–
OCH
3
NO
2
?
H
Cl
–
OCH
3
NO
2
Cl
H
NaI/acetone
OCH
3
NO
2
I
Correct option should be (1)
8. Ellingham diagram is a graphical
representation of :
(1) ?HvsT
(2) ?GvsP
(3) ?GvsT
(4)?? (G–T S)vsT
Answer (3)
Page 3


JEE (MAIN)-2021 : Phase-1(25-02-2021)-M
PART–B : CHEMISTRY
SECTION - I
Multiple Choice Questions: This section contains 20
multiple choice questions. Each question has 4
choices (1), (2), (3) and (4), out of which ONLY ONE
is correct.
Choose the correct answer :
1. Which one of the following reactions will not
form acetaldehyde?
(1)
-
??????? ?
32 4
CrO H SO
32
CH CH OH
(2)
= + ?????? ?
2
Pd(II)/Cu(II)
22 2
HO
CH CH O
(3) ? ??? ?
Cu
32
573 K
CH CH OH
(4)
?????? ?
2
(i) DIBAL-H
3
(ii) H O
CH CN
Answer (1)
Sol.
32 4
CrO H SO
32 3
Jones reagent
CH CH OH CH COOH
-
????????
In the rest of the options acetaldehyde will be
formed.
2. Given below are two statements:
Statement-I: CeO
2
 can be used for oxidation of
aldehyde and ketones.
Statement-II: Aqueous solution of EuSO
4
 is a
strong reducing agent.
In the light of the above statements, choose
the correct answer from the options given
below:
(1) Both Statement I and Statement II are false
(2) Both Statement I and Statement II are true
(3) Statement I is true but Statement II is false
(4) Statement I is false but Statement II is true
Answer (2)
Sol. Ce and Eu have stable oxidation state of +3.
So 
4
2
CeO
?
 acts as oxidizing agent to get
reduced to +3 and 
2
4
EuSO
?
 acts as reducing
agent to get oxidized to +3.
3. Given below are two statements:
Statement-I : An allotrope of oxygen is an
important intermediate in the formation of
reducing smog.
Statement-II: Gases such as oxides of nitrogen
and sulphur present in troposphere contribute
to the fomation of photochemical smog.
In the light of the above statements, choose
the correct answer from the options given
below:
(1) Statement I is true but Statement II is false
(2) Both Statement I and Statement II are false
(3) Statement I is false but Statement II is true
(4) Both Statement I and Statement II are true
Answer (2)
Sol.  Reducing smog is a mixture of smoke, fog
and sulphur dioxide. It does not involve O
3
(allotrope of oxygen) during its formation.
 The main component of the photochemical
smog result from the action of sunlight on
unsaturated hydrocarbons and nitrogen
oxides. No involvement of oxides of S.
So the answer should be, both statements
false.
4. Which of the glycosidic linkage between
galactose and glucose is present in lactose?
(1) C-1 of galactose and C-4 of glucose
(2) C-1 of glucose and C-6 of galactose
(3) C-1 of galactose and C-6 of glucose
(4) C-1 of glucose and C-4 of galactose
Answer (1)
Sol.
OO
HH
OH OH
OH
OH OH
HH
O
HO H
H
CH OH
2
CH OH
2
HH
HH
22
11
33
5
5
6 6
44
?-D-Galactose ?-D-Glucose
Lactose
A glycosidic linkage is between C1 of
?-D- galactose and C4 of ?-D-glucose.
So option-1 is the correct answer.
JEE (MAIN)-2021 : Phase-1(25-02-2021)-M
5. In which of the following pairs, the outer most
electronic configuration will be the same?
(1) Ni
2+ 
and Cu
+
(2) Fe
2+ 
and Co
+
(3) Cr
+ 
and Mn
2+
(4) V
2+ 
and Cr
+
Answer (3)
Sol.
Cr – 4 3d
+0 5
s
Mn s
2+ 0 5
 – 4 3d
have some electronic
configuration in the
outer most shell
6. The major product of the following chemical
reaction is:
3
2
42
1) H O ,
2)SOCl
32
3) Pd/BaSO ,H
CH CH CN ?
?
?
? ?????? ?
(1) CH
3
CH
2
CH
3
(2) CH
3
CH
2
CH
2
OH
(3) CH
3
CH
2
CHO
(4) (CH
3
CH
2
CO)
2
O
Answer (3)
Sol. CH
32
CH CN
HO
3
+
?
CH – CH – COOH
32
SOCl
2
CH – CH – C – Cl
32
O
O
CH – CH – C – H
32
Pd/BaSO , H
42
Correct option should be (3)
7. Identify A and B in the chemical reaction.
NO
2
OCH
3
?? ? ? ? ???? ?
HCl NaI
dryacetone
(major) major
[A] [B]
(1)
NO
2
OCH
3
Cl
A =
NO
2
OCH
3
I
B =
(2)
NO
2
OCH
3
Cl
A =
NO
2
OCH
3
Cl
B =
(3)
NO
2
OCH
3
Cl
A =
NO
2
I
Cl
B =
(4)
NO
2
OCH
3
Cl
A =
NO
2
I
Cl
B =
Answer (1)
Sol.
OCH
3
NO
2
HCl
+
–
OCH
3
NO
2
?
H
Cl
–
OCH
3
NO
2
Cl
H
NaI/acetone
OCH
3
NO
2
I
Correct option should be (1)
8. Ellingham diagram is a graphical
representation of :
(1) ?HvsT
(2) ?GvsP
(3) ?GvsT
(4)?? (G–T S)vsT
Answer (3)
JEE (MAIN)-2021 : Phase-1(25-02-2021)-M
Sol. Ellingham diagram is a graphical
representation of Gibbs energy ( ?G°) vs T
plots for the formation of the oxides.
Answer (3)
9. Compound(s) which will liberate carbon
dioxide with sodium bicarbonate solution is/
are :
OH
NH
2
A =
NH
2
NH
2
COOH
B =
C =
OH
NO
2
NO
2
NO
2
(1) B only (2) C only
(3) A and B only (4) B and C only
Answer (4)
Sol.
COOH
and
OH
NO
2
O
2
N NO
2
 are acidic
enough to liberate CO
2
 with NaHCO
3
 solution.
Answer (4)
10. In Freundlich adsorption isotherm at moderate
pressure, the extent of adsorption 
??
??
??
x
m
 is
directly proportional to P
x
. The value of x is:
(1) zero (2) 1
(3) ? (4)
1
n
Answer (4)
Sol. Freundlich adsorption isotherm can be plotted
using
 
1/n
x
kP
m
?
When pressure is moderate 
1/n
x
P
m
?
So, 
1
x
n
?
11. Identify A in the given chemical reaction.
CH
3
CH
2
CH
2
CH
2
CH
CH
3
CH
3
Mo O
23
773 K, 10-20 atm
‘A’
major product
(1)
(2)
CH
3
(3)
CH
3
(4)
Answer (2)
Sol.
CH
3
CH
2
CH
2
CH
2
CH
CH
3
Mo O
23
773 K, 10-20 atm
(A)
CH
3
CH
3
(Aromatisation)
12. According to molecular orbital theory, the
species among the following that does not
exist is
(1)
2
He
?
(2) Be
2
(3)
2
He
?
(4)
2
2
O
?
Answer (2)
Page 4


JEE (MAIN)-2021 : Phase-1(25-02-2021)-M
PART–B : CHEMISTRY
SECTION - I
Multiple Choice Questions: This section contains 20
multiple choice questions. Each question has 4
choices (1), (2), (3) and (4), out of which ONLY ONE
is correct.
Choose the correct answer :
1. Which one of the following reactions will not
form acetaldehyde?
(1)
-
??????? ?
32 4
CrO H SO
32
CH CH OH
(2)
= + ?????? ?
2
Pd(II)/Cu(II)
22 2
HO
CH CH O
(3) ? ??? ?
Cu
32
573 K
CH CH OH
(4)
?????? ?
2
(i) DIBAL-H
3
(ii) H O
CH CN
Answer (1)
Sol.
32 4
CrO H SO
32 3
Jones reagent
CH CH OH CH COOH
-
????????
In the rest of the options acetaldehyde will be
formed.
2. Given below are two statements:
Statement-I: CeO
2
 can be used for oxidation of
aldehyde and ketones.
Statement-II: Aqueous solution of EuSO
4
 is a
strong reducing agent.
In the light of the above statements, choose
the correct answer from the options given
below:
(1) Both Statement I and Statement II are false
(2) Both Statement I and Statement II are true
(3) Statement I is true but Statement II is false
(4) Statement I is false but Statement II is true
Answer (2)
Sol. Ce and Eu have stable oxidation state of +3.
So 
4
2
CeO
?
 acts as oxidizing agent to get
reduced to +3 and 
2
4
EuSO
?
 acts as reducing
agent to get oxidized to +3.
3. Given below are two statements:
Statement-I : An allotrope of oxygen is an
important intermediate in the formation of
reducing smog.
Statement-II: Gases such as oxides of nitrogen
and sulphur present in troposphere contribute
to the fomation of photochemical smog.
In the light of the above statements, choose
the correct answer from the options given
below:
(1) Statement I is true but Statement II is false
(2) Both Statement I and Statement II are false
(3) Statement I is false but Statement II is true
(4) Both Statement I and Statement II are true
Answer (2)
Sol.  Reducing smog is a mixture of smoke, fog
and sulphur dioxide. It does not involve O
3
(allotrope of oxygen) during its formation.
 The main component of the photochemical
smog result from the action of sunlight on
unsaturated hydrocarbons and nitrogen
oxides. No involvement of oxides of S.
So the answer should be, both statements
false.
4. Which of the glycosidic linkage between
galactose and glucose is present in lactose?
(1) C-1 of galactose and C-4 of glucose
(2) C-1 of glucose and C-6 of galactose
(3) C-1 of galactose and C-6 of glucose
(4) C-1 of glucose and C-4 of galactose
Answer (1)
Sol.
OO
HH
OH OH
OH
OH OH
HH
O
HO H
H
CH OH
2
CH OH
2
HH
HH
22
11
33
5
5
6 6
44
?-D-Galactose ?-D-Glucose
Lactose
A glycosidic linkage is between C1 of
?-D- galactose and C4 of ?-D-glucose.
So option-1 is the correct answer.
JEE (MAIN)-2021 : Phase-1(25-02-2021)-M
5. In which of the following pairs, the outer most
electronic configuration will be the same?
(1) Ni
2+ 
and Cu
+
(2) Fe
2+ 
and Co
+
(3) Cr
+ 
and Mn
2+
(4) V
2+ 
and Cr
+
Answer (3)
Sol.
Cr – 4 3d
+0 5
s
Mn s
2+ 0 5
 – 4 3d
have some electronic
configuration in the
outer most shell
6. The major product of the following chemical
reaction is:
3
2
42
1) H O ,
2)SOCl
32
3) Pd/BaSO ,H
CH CH CN ?
?
?
? ?????? ?
(1) CH
3
CH
2
CH
3
(2) CH
3
CH
2
CH
2
OH
(3) CH
3
CH
2
CHO
(4) (CH
3
CH
2
CO)
2
O
Answer (3)
Sol. CH
32
CH CN
HO
3
+
?
CH – CH – COOH
32
SOCl
2
CH – CH – C – Cl
32
O
O
CH – CH – C – H
32
Pd/BaSO , H
42
Correct option should be (3)
7. Identify A and B in the chemical reaction.
NO
2
OCH
3
?? ? ? ? ???? ?
HCl NaI
dryacetone
(major) major
[A] [B]
(1)
NO
2
OCH
3
Cl
A =
NO
2
OCH
3
I
B =
(2)
NO
2
OCH
3
Cl
A =
NO
2
OCH
3
Cl
B =
(3)
NO
2
OCH
3
Cl
A =
NO
2
I
Cl
B =
(4)
NO
2
OCH
3
Cl
A =
NO
2
I
Cl
B =
Answer (1)
Sol.
OCH
3
NO
2
HCl
+
–
OCH
3
NO
2
?
H
Cl
–
OCH
3
NO
2
Cl
H
NaI/acetone
OCH
3
NO
2
I
Correct option should be (1)
8. Ellingham diagram is a graphical
representation of :
(1) ?HvsT
(2) ?GvsP
(3) ?GvsT
(4)?? (G–T S)vsT
Answer (3)
JEE (MAIN)-2021 : Phase-1(25-02-2021)-M
Sol. Ellingham diagram is a graphical
representation of Gibbs energy ( ?G°) vs T
plots for the formation of the oxides.
Answer (3)
9. Compound(s) which will liberate carbon
dioxide with sodium bicarbonate solution is/
are :
OH
NH
2
A =
NH
2
NH
2
COOH
B =
C =
OH
NO
2
NO
2
NO
2
(1) B only (2) C only
(3) A and B only (4) B and C only
Answer (4)
Sol.
COOH
and
OH
NO
2
O
2
N NO
2
 are acidic
enough to liberate CO
2
 with NaHCO
3
 solution.
Answer (4)
10. In Freundlich adsorption isotherm at moderate
pressure, the extent of adsorption 
??
??
??
x
m
 is
directly proportional to P
x
. The value of x is:
(1) zero (2) 1
(3) ? (4)
1
n
Answer (4)
Sol. Freundlich adsorption isotherm can be plotted
using
 
1/n
x
kP
m
?
When pressure is moderate 
1/n
x
P
m
?
So, 
1
x
n
?
11. Identify A in the given chemical reaction.
CH
3
CH
2
CH
2
CH
2
CH
CH
3
CH
3
Mo O
23
773 K, 10-20 atm
‘A’
major product
(1)
(2)
CH
3
(3)
CH
3
(4)
Answer (2)
Sol.
CH
3
CH
2
CH
2
CH
2
CH
CH
3
Mo O
23
773 K, 10-20 atm
(A)
CH
3
CH
3
(Aromatisation)
12. According to molecular orbital theory, the
species among the following that does not
exist is
(1)
2
He
?
(2) Be
2
(3)
2
He
?
(4)
2
2
O
?
Answer (2)
JEE (MAIN)-2021 : Phase-1(25-02-2021)-M
Sol. Species with bond order equal to zero will not
exist.
Species Bond order
2
He
?
0.5
Be
2
0
2
He
?
0.5
2
2
O
?
1
13. The plots of radial distribution functions for
various orbitals of hydrogen atom against ‘r’
are given below
(A)
8
4
0
5
r(Å)
10
4rR (r) ?
2 2
n, l
(B)
3
2
0
5
r(Å)
10
4rR (r) ?
2 2
n, l
1
(C)
3
2
0
5
r(Å)
10
4rR (r) ?
2 2
n, l
1
(D)
2.0
0
5
r(Å)
10
4rR (r) ?
2 2
n, l
1.5
1.0
0.5
The correct plot for 3s orbital is
(1) (C)
(2) (D)
(3) (B)
(4) (A)
Answer (2)
Sol. 3s orbital has 2 radial nodes
Number of radial nodes = n – (l + 1)
? Graph (A) can be for 1s
Graph (B) can be for 2s
Graph (C) can be for 2p
Graph (D) can be for 3s
14. The solubility of AgCN in a buffer solution of
pH = 3 is x. The value of x is :
[Assume : No cyano complex is formed;
K
sp
(AgCN) = 2.2 × 10
–16
 and K
a
(HCN) =
6.2 × 10
–10
]
(1) 1.9 × 10
–5
(2) 1.6 × 10
–6
(3) 2.2 × 10
–16
(4) 0.625 × 10
–6
Answer (1)
Sol. AgCN 

 Ag
+
 + CN
–
CN
–
 + H
3
O
+
 

 HCN + H
2
O
let solubility of AgCN = x molar
??
?
a
[H ][CN ]
k
[HCN]
?
??
6
[HCN]
1.6 10
[CN ]
As each CN
–
 ion hydrolyses to give one HCN
x = [Ag
+
] = [CN
–
] + [HCN]
? [CN
–
] << [HCN]
? x = [Ag
+
] ? [HCN]
?
?
?
6
x
[CN ]
1.6 10
K
sp
 = [Ag
+
][CN
–
]
?
??
?
2
16
6
x
2.2 10
1.6 10
x ? 1.9 × 10
–5
 M
15. The hybridization and magnetic nature of
[Mn(CN)
6
]
4–
 and [Fe(CN)
6
]
3–
, respectively are
(1) d
2
sp
3
 and paramagnetic
(2) d
2
sp
3
 and diamagnetic
(3) sp
3
d
2
 and paramagnetic
(4) sp
3
d
2
 and diamagnetic
Answer (1)
Page 5


JEE (MAIN)-2021 : Phase-1(25-02-2021)-M
PART–B : CHEMISTRY
SECTION - I
Multiple Choice Questions: This section contains 20
multiple choice questions. Each question has 4
choices (1), (2), (3) and (4), out of which ONLY ONE
is correct.
Choose the correct answer :
1. Which one of the following reactions will not
form acetaldehyde?
(1)
-
??????? ?
32 4
CrO H SO
32
CH CH OH
(2)
= + ?????? ?
2
Pd(II)/Cu(II)
22 2
HO
CH CH O
(3) ? ??? ?
Cu
32
573 K
CH CH OH
(4)
?????? ?
2
(i) DIBAL-H
3
(ii) H O
CH CN
Answer (1)
Sol.
32 4
CrO H SO
32 3
Jones reagent
CH CH OH CH COOH
-
????????
In the rest of the options acetaldehyde will be
formed.
2. Given below are two statements:
Statement-I: CeO
2
 can be used for oxidation of
aldehyde and ketones.
Statement-II: Aqueous solution of EuSO
4
 is a
strong reducing agent.
In the light of the above statements, choose
the correct answer from the options given
below:
(1) Both Statement I and Statement II are false
(2) Both Statement I and Statement II are true
(3) Statement I is true but Statement II is false
(4) Statement I is false but Statement II is true
Answer (2)
Sol. Ce and Eu have stable oxidation state of +3.
So 
4
2
CeO
?
 acts as oxidizing agent to get
reduced to +3 and 
2
4
EuSO
?
 acts as reducing
agent to get oxidized to +3.
3. Given below are two statements:
Statement-I : An allotrope of oxygen is an
important intermediate in the formation of
reducing smog.
Statement-II: Gases such as oxides of nitrogen
and sulphur present in troposphere contribute
to the fomation of photochemical smog.
In the light of the above statements, choose
the correct answer from the options given
below:
(1) Statement I is true but Statement II is false
(2) Both Statement I and Statement II are false
(3) Statement I is false but Statement II is true
(4) Both Statement I and Statement II are true
Answer (2)
Sol.  Reducing smog is a mixture of smoke, fog
and sulphur dioxide. It does not involve O
3
(allotrope of oxygen) during its formation.
 The main component of the photochemical
smog result from the action of sunlight on
unsaturated hydrocarbons and nitrogen
oxides. No involvement of oxides of S.
So the answer should be, both statements
false.
4. Which of the glycosidic linkage between
galactose and glucose is present in lactose?
(1) C-1 of galactose and C-4 of glucose
(2) C-1 of glucose and C-6 of galactose
(3) C-1 of galactose and C-6 of glucose
(4) C-1 of glucose and C-4 of galactose
Answer (1)
Sol.
OO
HH
OH OH
OH
OH OH
HH
O
HO H
H
CH OH
2
CH OH
2
HH
HH
22
11
33
5
5
6 6
44
?-D-Galactose ?-D-Glucose
Lactose
A glycosidic linkage is between C1 of
?-D- galactose and C4 of ?-D-glucose.
So option-1 is the correct answer.
JEE (MAIN)-2021 : Phase-1(25-02-2021)-M
5. In which of the following pairs, the outer most
electronic configuration will be the same?
(1) Ni
2+ 
and Cu
+
(2) Fe
2+ 
and Co
+
(3) Cr
+ 
and Mn
2+
(4) V
2+ 
and Cr
+
Answer (3)
Sol.
Cr – 4 3d
+0 5
s
Mn s
2+ 0 5
 – 4 3d
have some electronic
configuration in the
outer most shell
6. The major product of the following chemical
reaction is:
3
2
42
1) H O ,
2)SOCl
32
3) Pd/BaSO ,H
CH CH CN ?
?
?
? ?????? ?
(1) CH
3
CH
2
CH
3
(2) CH
3
CH
2
CH
2
OH
(3) CH
3
CH
2
CHO
(4) (CH
3
CH
2
CO)
2
O
Answer (3)
Sol. CH
32
CH CN
HO
3
+
?
CH – CH – COOH
32
SOCl
2
CH – CH – C – Cl
32
O
O
CH – CH – C – H
32
Pd/BaSO , H
42
Correct option should be (3)
7. Identify A and B in the chemical reaction.
NO
2
OCH
3
?? ? ? ? ???? ?
HCl NaI
dryacetone
(major) major
[A] [B]
(1)
NO
2
OCH
3
Cl
A =
NO
2
OCH
3
I
B =
(2)
NO
2
OCH
3
Cl
A =
NO
2
OCH
3
Cl
B =
(3)
NO
2
OCH
3
Cl
A =
NO
2
I
Cl
B =
(4)
NO
2
OCH
3
Cl
A =
NO
2
I
Cl
B =
Answer (1)
Sol.
OCH
3
NO
2
HCl
+
–
OCH
3
NO
2
?
H
Cl
–
OCH
3
NO
2
Cl
H
NaI/acetone
OCH
3
NO
2
I
Correct option should be (1)
8. Ellingham diagram is a graphical
representation of :
(1) ?HvsT
(2) ?GvsP
(3) ?GvsT
(4)?? (G–T S)vsT
Answer (3)
JEE (MAIN)-2021 : Phase-1(25-02-2021)-M
Sol. Ellingham diagram is a graphical
representation of Gibbs energy ( ?G°) vs T
plots for the formation of the oxides.
Answer (3)
9. Compound(s) which will liberate carbon
dioxide with sodium bicarbonate solution is/
are :
OH
NH
2
A =
NH
2
NH
2
COOH
B =
C =
OH
NO
2
NO
2
NO
2
(1) B only (2) C only
(3) A and B only (4) B and C only
Answer (4)
Sol.
COOH
and
OH
NO
2
O
2
N NO
2
 are acidic
enough to liberate CO
2
 with NaHCO
3
 solution.
Answer (4)
10. In Freundlich adsorption isotherm at moderate
pressure, the extent of adsorption 
??
??
??
x
m
 is
directly proportional to P
x
. The value of x is:
(1) zero (2) 1
(3) ? (4)
1
n
Answer (4)
Sol. Freundlich adsorption isotherm can be plotted
using
 
1/n
x
kP
m
?
When pressure is moderate 
1/n
x
P
m
?
So, 
1
x
n
?
11. Identify A in the given chemical reaction.
CH
3
CH
2
CH
2
CH
2
CH
CH
3
CH
3
Mo O
23
773 K, 10-20 atm
‘A’
major product
(1)
(2)
CH
3
(3)
CH
3
(4)
Answer (2)
Sol.
CH
3
CH
2
CH
2
CH
2
CH
CH
3
Mo O
23
773 K, 10-20 atm
(A)
CH
3
CH
3
(Aromatisation)
12. According to molecular orbital theory, the
species among the following that does not
exist is
(1)
2
He
?
(2) Be
2
(3)
2
He
?
(4)
2
2
O
?
Answer (2)
JEE (MAIN)-2021 : Phase-1(25-02-2021)-M
Sol. Species with bond order equal to zero will not
exist.
Species Bond order
2
He
?
0.5
Be
2
0
2
He
?
0.5
2
2
O
?
1
13. The plots of radial distribution functions for
various orbitals of hydrogen atom against ‘r’
are given below
(A)
8
4
0
5
r(Å)
10
4rR (r) ?
2 2
n, l
(B)
3
2
0
5
r(Å)
10
4rR (r) ?
2 2
n, l
1
(C)
3
2
0
5
r(Å)
10
4rR (r) ?
2 2
n, l
1
(D)
2.0
0
5
r(Å)
10
4rR (r) ?
2 2
n, l
1.5
1.0
0.5
The correct plot for 3s orbital is
(1) (C)
(2) (D)
(3) (B)
(4) (A)
Answer (2)
Sol. 3s orbital has 2 radial nodes
Number of radial nodes = n – (l + 1)
? Graph (A) can be for 1s
Graph (B) can be for 2s
Graph (C) can be for 2p
Graph (D) can be for 3s
14. The solubility of AgCN in a buffer solution of
pH = 3 is x. The value of x is :
[Assume : No cyano complex is formed;
K
sp
(AgCN) = 2.2 × 10
–16
 and K
a
(HCN) =
6.2 × 10
–10
]
(1) 1.9 × 10
–5
(2) 1.6 × 10
–6
(3) 2.2 × 10
–16
(4) 0.625 × 10
–6
Answer (1)
Sol. AgCN 

 Ag
+
 + CN
–
CN
–
 + H
3
O
+
 

 HCN + H
2
O
let solubility of AgCN = x molar
??
?
a
[H ][CN ]
k
[HCN]
?
??
6
[HCN]
1.6 10
[CN ]
As each CN
–
 ion hydrolyses to give one HCN
x = [Ag
+
] = [CN
–
] + [HCN]
? [CN
–
] << [HCN]
? x = [Ag
+
] ? [HCN]
?
?
?
6
x
[CN ]
1.6 10
K
sp
 = [Ag
+
][CN
–
]
?
??
?
2
16
6
x
2.2 10
1.6 10
x ? 1.9 × 10
–5
 M
15. The hybridization and magnetic nature of
[Mn(CN)
6
]
4–
 and [Fe(CN)
6
]
3–
, respectively are
(1) d
2
sp
3
 and paramagnetic
(2) d
2
sp
3
 and diamagnetic
(3) sp
3
d
2
 and paramagnetic
(4) sp
3
d
2
 and diamagnetic
Answer (1)
JEE (MAIN)-2021 : Phase-1(25-02-2021)-M
Sol. [Mn(CN)
6
]
4–
Mn
2+
 = 3d
5
 4s
0
–
CN is a strong field ligand
? Pairing will occur
:: : : ::
dsp
23
Paramagnetic
[Fe(CN)
6
]
3–
Fe
3+
 = 3d
5
 4s
0
CN
–
 is a strong field ligand
? Pairing will occur
:: : : : :
dsp
23
Paramagnetic
16. Complete combustion of 1.80 g of an oxygen
containing compound (C
x
H
y
O
z
) gave 2.64 g of
CO
2
 and 1.08 g of H
2
O. The percentage of
oxygen in the organic compound is :
(1) 50.33
(2) 53.33
(3) 51.63
(4) 63.53
Answer (2)
Sol.
xy z 2 2 2
y
CHO O xCO HO
2
?? ?
2.64 g of CO
2
 contains  0.72 g C.
1.08 g of H
2
O contains 0.12 g H.
? mass  of oxygen present = 1.80 – (0.72
+0.12) = 0.96 g
% of O = 
0.96
100
1.80
?
 = 53.33 %
17. Which of the following equation depicts the
oxidizing nature of H
2
O
2
?
(1) 2I
–
 + H
2
O
2
 + 2H
+
 ? I
2
 + 2H
2
O
(2) KIO
4
 + H
2
O
2
 ? KIO
3
 + H
2
O + O
2
(3) Cl
2
 + H
2
O
2
 ? 2HCI + O
2
(4) I
2
 + H
2
O
2
 + 2OH
–
 ? 2I
–
 + 2H
2
O + O
2
Answer (1)
Sol.
1
10 2
–
22 2 2
2I H O 2H I 2H O
?
??
?
?? ??
I is oxidised from –1 to 0 oxidation state.
18. Which statement is correct?
(1)Buna-S is a synthetic and linear
thermosetting polymer.
(2) Buna-N is a natural polymer.
(3) Synthesis of Buna-S needs nascent
oxygen.
(4) Neoprene is an addition copolymer used in
plastic bucket manufacturing.
Answer (3)
So. ? Buna-S is an elastomer
? Buna-N is a synthetic polymer
? Buna-S is polymerised by addition
polymerisation method which needs
radical initiator for chain propagation step.
Nascent oxygen can be used as an Radical
initiator.
? Neoprene is a synthetic rubber.
19. Which of the following reaction/s will not give
p-aminoazobenzene?
A. 
NO
2
(ii) HNO
2
(iii) Aniline
(i) Sn/HCl
B.
NO
2
(ii) NaOH
(iii) Aniline
(i) NaBH
4
C.
NH
2
(i) HNO
2
(ii) Aniline, HCl
(1) C only
(2) B only
(3) A only
(4) A and B
Answer (2)
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