Solutions: JEE Mains Previous Year Questions (2021-2024) | Chemistry for JEE Main & Advanced PDF Download

 Page 1


JEE Mains Previous Year Questions 
(2021-2024): Solutions 
2024 
Q1: We have three aqueous solutions of ???????? labelled as ' ?? ,' ' ?? ' and ' ?? ' with concentration 
?? . ???? , ?? . ?????? and ?? . ???????? , respectively. The value of van ' ?? Hoff factor(i) for these solutions will be 
in the order: 
A. ?? ?? < ?? ?? < ?? ?? 
B. ?? ?? < ?? ?? < ?? ?? 
C. ?? ?? > ?? ?? > ?? ?? 
D. ?? ?? = ?? ?? = ?? ??   [JEE Main 2024 (Online) 1st February Morning Shift] 
Ans: (b) 
 
Salt Values of i (for different conc. of a Salt) 
NaCl 0.1M 0.01M 0.001M 
 1.87 1.94 1.94 
 
The van 't Hoff factor (i) is used to describe the number of particles a solute formula unit produces in a 
solution. For an electrolyte like NaCl, which dissociates completely in very dilute solutions, the 
theoretical value of ?? is approximately 2, since NaCl dissociates into Na
+
and Cl
-
ions. 
In real scenarios, as the concentration of the solution decreases (making the solution more dilute), the 
interaction between the ions decreases, allowing more complete dissociation. Therefore, for practical 
purposes, the van 't Hoff factor ?? approaches its theoretical maximum value as concentration decreases. 
Thus, for NaCl solutions of concentrations 0.1M, 0.01M, and 0.001M, the fact that NaCl dissociates 
more completely in more dilute solutions implies that ?? increases with decreasing concentration. 
Hence, the order of ?? based on the concentration would be i
A
< i
B
< i
C
, as concentration 0.1M >
0.01M > 0.001M, respectively. Thus, option B correctly describes the order of the van 't Hoff factors for 
these solutions. 
Q2: Identify the mixture that shows positive deviations from Raoult's Law 
A. (????
?? )
?? ???? + ????
?? 
B. (????
?? )
?? ???? + ?? ?? ?? ?? ????
?? 
C. ???????? ?? + ?? ?? ?? ?? 
D. ???????? ?? + (????
?? )
?? ????    [JEE Main 2024 (Online) 31st January Morning Shift] 
Page 2


JEE Mains Previous Year Questions 
(2021-2024): Solutions 
2024 
Q1: We have three aqueous solutions of ???????? labelled as ' ?? ,' ' ?? ' and ' ?? ' with concentration 
?? . ???? , ?? . ?????? and ?? . ???????? , respectively. The value of van ' ?? Hoff factor(i) for these solutions will be 
in the order: 
A. ?? ?? < ?? ?? < ?? ?? 
B. ?? ?? < ?? ?? < ?? ?? 
C. ?? ?? > ?? ?? > ?? ?? 
D. ?? ?? = ?? ?? = ?? ??   [JEE Main 2024 (Online) 1st February Morning Shift] 
Ans: (b) 
 
Salt Values of i (for different conc. of a Salt) 
NaCl 0.1M 0.01M 0.001M 
 1.87 1.94 1.94 
 
The van 't Hoff factor (i) is used to describe the number of particles a solute formula unit produces in a 
solution. For an electrolyte like NaCl, which dissociates completely in very dilute solutions, the 
theoretical value of ?? is approximately 2, since NaCl dissociates into Na
+
and Cl
-
ions. 
In real scenarios, as the concentration of the solution decreases (making the solution more dilute), the 
interaction between the ions decreases, allowing more complete dissociation. Therefore, for practical 
purposes, the van 't Hoff factor ?? approaches its theoretical maximum value as concentration decreases. 
Thus, for NaCl solutions of concentrations 0.1M, 0.01M, and 0.001M, the fact that NaCl dissociates 
more completely in more dilute solutions implies that ?? increases with decreasing concentration. 
Hence, the order of ?? based on the concentration would be i
A
< i
B
< i
C
, as concentration 0.1M >
0.01M > 0.001M, respectively. Thus, option B correctly describes the order of the van 't Hoff factors for 
these solutions. 
Q2: Identify the mixture that shows positive deviations from Raoult's Law 
A. (????
?? )
?? ???? + ????
?? 
B. (????
?? )
?? ???? + ?? ?? ?? ?? ????
?? 
C. ???????? ?? + ?? ?? ?? ?? 
D. ???????? ?? + (????
?? )
?? ????    [JEE Main 2024 (Online) 31st January Morning Shift] 
Ans: (a) 
(CH
3
)
2
CO + CS
2
 Exibits positive deviations from Raoult's Law. 
Q3: Match List I with List II 
 List - 1 (Technique)  List - II (Application 
(A) Distillation (I) 
Separation of glycerol 
from spent-lye 
 
(B) Fractional distillation (II) Aniline - Water mixture 
(C) Steam distillation (iII) 
Separation of crude oil 
fractions 
 
(D) 
Distillation under reduced 
pressure 
 
(?? ) Chloroform - Aniline 
Choose the correct answer from the options given below: 
A. A-I, B-II, C-IV, D-III 
B. A-II, B-III, C-I, D-IV 
C. A-IV, B-I, C-II, D-III 
D. A-IV, B-III, C-II, D-I     [JEE Main 2024 (Online) 31st January Morning Shift] 
Ans: In order to match the techniques listed in List I with their corresponding applications in List II, we 
need to understand what each technique is generally used for: 
Distillation: A process used to separate components in a liquid mixture by selective evaporation and 
condensation. It is used for mixtures where the components have significantly different boiling points. 
Fractional distillation: An advanced form of distillation used when the boiling points of the components 
are closer. It involves the use of a fractionating column, which allows for multiple simple distillations to 
occur within the column, hence separating components with similar boiling points. 
Steam distillation: Used to purify temperature-sensitive materials, like organic compounds, that might 
decompose at higher temperatures. This process allows distillation at temperatures below the 
substances' regular boiling points. 
Distillation under reduced pressure (Vacuum distillation): Used for substances that may decompose or 
react at high temperatures. By reducing the pressure, the boiling points of the components are reduced, 
allowing distillation to proceed at lower temperatures. 
Page 3


JEE Mains Previous Year Questions 
(2021-2024): Solutions 
2024 
Q1: We have three aqueous solutions of ???????? labelled as ' ?? ,' ' ?? ' and ' ?? ' with concentration 
?? . ???? , ?? . ?????? and ?? . ???????? , respectively. The value of van ' ?? Hoff factor(i) for these solutions will be 
in the order: 
A. ?? ?? < ?? ?? < ?? ?? 
B. ?? ?? < ?? ?? < ?? ?? 
C. ?? ?? > ?? ?? > ?? ?? 
D. ?? ?? = ?? ?? = ?? ??   [JEE Main 2024 (Online) 1st February Morning Shift] 
Ans: (b) 
 
Salt Values of i (for different conc. of a Salt) 
NaCl 0.1M 0.01M 0.001M 
 1.87 1.94 1.94 
 
The van 't Hoff factor (i) is used to describe the number of particles a solute formula unit produces in a 
solution. For an electrolyte like NaCl, which dissociates completely in very dilute solutions, the 
theoretical value of ?? is approximately 2, since NaCl dissociates into Na
+
and Cl
-
ions. 
In real scenarios, as the concentration of the solution decreases (making the solution more dilute), the 
interaction between the ions decreases, allowing more complete dissociation. Therefore, for practical 
purposes, the van 't Hoff factor ?? approaches its theoretical maximum value as concentration decreases. 
Thus, for NaCl solutions of concentrations 0.1M, 0.01M, and 0.001M, the fact that NaCl dissociates 
more completely in more dilute solutions implies that ?? increases with decreasing concentration. 
Hence, the order of ?? based on the concentration would be i
A
< i
B
< i
C
, as concentration 0.1M >
0.01M > 0.001M, respectively. Thus, option B correctly describes the order of the van 't Hoff factors for 
these solutions. 
Q2: Identify the mixture that shows positive deviations from Raoult's Law 
A. (????
?? )
?? ???? + ????
?? 
B. (????
?? )
?? ???? + ?? ?? ?? ?? ????
?? 
C. ???????? ?? + ?? ?? ?? ?? 
D. ???????? ?? + (????
?? )
?? ????    [JEE Main 2024 (Online) 31st January Morning Shift] 
Ans: (a) 
(CH
3
)
2
CO + CS
2
 Exibits positive deviations from Raoult's Law. 
Q3: Match List I with List II 
 List - 1 (Technique)  List - II (Application 
(A) Distillation (I) 
Separation of glycerol 
from spent-lye 
 
(B) Fractional distillation (II) Aniline - Water mixture 
(C) Steam distillation (iII) 
Separation of crude oil 
fractions 
 
(D) 
Distillation under reduced 
pressure 
 
(?? ) Chloroform - Aniline 
Choose the correct answer from the options given below: 
A. A-I, B-II, C-IV, D-III 
B. A-II, B-III, C-I, D-IV 
C. A-IV, B-I, C-II, D-III 
D. A-IV, B-III, C-II, D-I     [JEE Main 2024 (Online) 31st January Morning Shift] 
Ans: In order to match the techniques listed in List I with their corresponding applications in List II, we 
need to understand what each technique is generally used for: 
Distillation: A process used to separate components in a liquid mixture by selective evaporation and 
condensation. It is used for mixtures where the components have significantly different boiling points. 
Fractional distillation: An advanced form of distillation used when the boiling points of the components 
are closer. It involves the use of a fractionating column, which allows for multiple simple distillations to 
occur within the column, hence separating components with similar boiling points. 
Steam distillation: Used to purify temperature-sensitive materials, like organic compounds, that might 
decompose at higher temperatures. This process allows distillation at temperatures below the 
substances' regular boiling points. 
Distillation under reduced pressure (Vacuum distillation): Used for substances that may decompose or 
react at high temperatures. By reducing the pressure, the boiling points of the components are reduced, 
allowing distillation to proceed at lower temperatures. 
Now applying this knowledge to the applications provided in List II: 
Separation of glycerol from spent-lye: This is typically done by simple distillation since glycerol and 
water (spent-lye) have a sufficiently large difference in boiling points. 
Aniline - Water mixture: Since aniline and water form an azeotrope, they have very similar boiling 
points, and separation would typically require fractional distillation. 
Separation of crude oil fractions: Fractional distillation is used to separate various components of crude 
oil due to the narrow differences in their boiling points. 
Chloroform - Aniline: These compounds have significantly different boiling points, so a simple distillation 
could be used, but since aniline can be heat sensitive, distillation under reduced pressure would be the 
best choice to prevent its decomposition. 
Having established the appropriate method for each application, we can match List I with List II: 
(A) Distillation ? (I) Separation of glycerol from spent-lye 
(B) Fractional distillation ? (III) Separation of crude oil fractions 
(C) Steam distillation ? (II) Aniline - Water mixture 
(D) Distillation under reduced pressure ? (IV) Chloroform - Aniline 
Therefore, the correct option that matches List I (Technique) with the proper application in List II is: 
Option D A-IV, B-III, C-II, D-I 
Q4: The solution from the following with highest depression in freezing point/lowest freezing point is 
A. ?????? ?? of acetic acid dissolved in benzene 
B. ?????? ?? of acetic acid dissolved in water 
C. ?????? ?? of benzoic acid dissolved in benzene 
D. ?????? ?? of glucose dissolved in water    [JEE Main 2024 (Online) 30th January Evening Shift] 
Ans: (b) 
?T
f
 is maximum when i × m is maximum. 
1 m
1
=
180
60
= 3, i = 1 + ?? 
Hence 
?T
f
= (1 + ?? ) · k
f
= 3 × 1.86 = 5.58
°
C(?? << 1) 
2 m
2
=
180
60
= 3, i = 0.5, ?T
f
=
3
2
× k
f
'
= 7.68
°
C 
3 m
3
=
180
122
= 1.48, i = 0.5, ?T
f
=
1.48
2
× k
f
 
'
= 3.8
°
C 
4 m
4
=
180
180
= 1, i = 1, ?T
f
= 1 · k
f
 
'
= 1.86
°
C 
As per NCERT, k
f
 
'
(H
2
O) = 1.86k · kgmol
-1
 
k
f
 
'
( Benzene ) = 5.12k · kgmol
-1
 
Q5: What happens to freezing point of benzene when small quantity of napthalene is added to 
benzene? 
Page 4


JEE Mains Previous Year Questions 
(2021-2024): Solutions 
2024 
Q1: We have three aqueous solutions of ???????? labelled as ' ?? ,' ' ?? ' and ' ?? ' with concentration 
?? . ???? , ?? . ?????? and ?? . ???????? , respectively. The value of van ' ?? Hoff factor(i) for these solutions will be 
in the order: 
A. ?? ?? < ?? ?? < ?? ?? 
B. ?? ?? < ?? ?? < ?? ?? 
C. ?? ?? > ?? ?? > ?? ?? 
D. ?? ?? = ?? ?? = ?? ??   [JEE Main 2024 (Online) 1st February Morning Shift] 
Ans: (b) 
 
Salt Values of i (for different conc. of a Salt) 
NaCl 0.1M 0.01M 0.001M 
 1.87 1.94 1.94 
 
The van 't Hoff factor (i) is used to describe the number of particles a solute formula unit produces in a 
solution. For an electrolyte like NaCl, which dissociates completely in very dilute solutions, the 
theoretical value of ?? is approximately 2, since NaCl dissociates into Na
+
and Cl
-
ions. 
In real scenarios, as the concentration of the solution decreases (making the solution more dilute), the 
interaction between the ions decreases, allowing more complete dissociation. Therefore, for practical 
purposes, the van 't Hoff factor ?? approaches its theoretical maximum value as concentration decreases. 
Thus, for NaCl solutions of concentrations 0.1M, 0.01M, and 0.001M, the fact that NaCl dissociates 
more completely in more dilute solutions implies that ?? increases with decreasing concentration. 
Hence, the order of ?? based on the concentration would be i
A
< i
B
< i
C
, as concentration 0.1M >
0.01M > 0.001M, respectively. Thus, option B correctly describes the order of the van 't Hoff factors for 
these solutions. 
Q2: Identify the mixture that shows positive deviations from Raoult's Law 
A. (????
?? )
?? ???? + ????
?? 
B. (????
?? )
?? ???? + ?? ?? ?? ?? ????
?? 
C. ???????? ?? + ?? ?? ?? ?? 
D. ???????? ?? + (????
?? )
?? ????    [JEE Main 2024 (Online) 31st January Morning Shift] 
Ans: (a) 
(CH
3
)
2
CO + CS
2
 Exibits positive deviations from Raoult's Law. 
Q3: Match List I with List II 
 List - 1 (Technique)  List - II (Application 
(A) Distillation (I) 
Separation of glycerol 
from spent-lye 
 
(B) Fractional distillation (II) Aniline - Water mixture 
(C) Steam distillation (iII) 
Separation of crude oil 
fractions 
 
(D) 
Distillation under reduced 
pressure 
 
(?? ) Chloroform - Aniline 
Choose the correct answer from the options given below: 
A. A-I, B-II, C-IV, D-III 
B. A-II, B-III, C-I, D-IV 
C. A-IV, B-I, C-II, D-III 
D. A-IV, B-III, C-II, D-I     [JEE Main 2024 (Online) 31st January Morning Shift] 
Ans: In order to match the techniques listed in List I with their corresponding applications in List II, we 
need to understand what each technique is generally used for: 
Distillation: A process used to separate components in a liquid mixture by selective evaporation and 
condensation. It is used for mixtures where the components have significantly different boiling points. 
Fractional distillation: An advanced form of distillation used when the boiling points of the components 
are closer. It involves the use of a fractionating column, which allows for multiple simple distillations to 
occur within the column, hence separating components with similar boiling points. 
Steam distillation: Used to purify temperature-sensitive materials, like organic compounds, that might 
decompose at higher temperatures. This process allows distillation at temperatures below the 
substances' regular boiling points. 
Distillation under reduced pressure (Vacuum distillation): Used for substances that may decompose or 
react at high temperatures. By reducing the pressure, the boiling points of the components are reduced, 
allowing distillation to proceed at lower temperatures. 
Now applying this knowledge to the applications provided in List II: 
Separation of glycerol from spent-lye: This is typically done by simple distillation since glycerol and 
water (spent-lye) have a sufficiently large difference in boiling points. 
Aniline - Water mixture: Since aniline and water form an azeotrope, they have very similar boiling 
points, and separation would typically require fractional distillation. 
Separation of crude oil fractions: Fractional distillation is used to separate various components of crude 
oil due to the narrow differences in their boiling points. 
Chloroform - Aniline: These compounds have significantly different boiling points, so a simple distillation 
could be used, but since aniline can be heat sensitive, distillation under reduced pressure would be the 
best choice to prevent its decomposition. 
Having established the appropriate method for each application, we can match List I with List II: 
(A) Distillation ? (I) Separation of glycerol from spent-lye 
(B) Fractional distillation ? (III) Separation of crude oil fractions 
(C) Steam distillation ? (II) Aniline - Water mixture 
(D) Distillation under reduced pressure ? (IV) Chloroform - Aniline 
Therefore, the correct option that matches List I (Technique) with the proper application in List II is: 
Option D A-IV, B-III, C-II, D-I 
Q4: The solution from the following with highest depression in freezing point/lowest freezing point is 
A. ?????? ?? of acetic acid dissolved in benzene 
B. ?????? ?? of acetic acid dissolved in water 
C. ?????? ?? of benzoic acid dissolved in benzene 
D. ?????? ?? of glucose dissolved in water    [JEE Main 2024 (Online) 30th January Evening Shift] 
Ans: (b) 
?T
f
 is maximum when i × m is maximum. 
1 m
1
=
180
60
= 3, i = 1 + ?? 
Hence 
?T
f
= (1 + ?? ) · k
f
= 3 × 1.86 = 5.58
°
C(?? << 1) 
2 m
2
=
180
60
= 3, i = 0.5, ?T
f
=
3
2
× k
f
'
= 7.68
°
C 
3 m
3
=
180
122
= 1.48, i = 0.5, ?T
f
=
1.48
2
× k
f
 
'
= 3.8
°
C 
4 m
4
=
180
180
= 1, i = 1, ?T
f
= 1 · k
f
 
'
= 1.86
°
C 
As per NCERT, k
f
 
'
(H
2
O) = 1.86k · kgmol
-1
 
k
f
 
'
( Benzene ) = 5.12k · kgmol
-1
 
Q5: What happens to freezing point of benzene when small quantity of napthalene is added to 
benzene? 
A. Increases 
B. Decreases 
C. Remains unchanged 
D. First decreases and then increases     [JEE Main 2024 (Online) 30th January Morning Shift] 
Ans: (b) 
On addition of naphthalene to benzene there is depression in freezing point of benzene. 
Q6: A solution of two miscible liquids showing negative deviation from Raoult's law will have: 
A. increased vapour pressure, increased boiling point 
B. increased vapour pressure, decreased boiling point 
C. decreased vapour pressure, decreased boiling point 
D. decreased vapour pressure, increased boiling point    [JEE Main 2024 (Online) 27th January Morning 
Shift] 
Ans: (d) 
Negative Deviation from Raoult's Law 
Negative deviation means the intermolecular forces of attraction between the molecules of the two 
liquids (A-B) are stronger than the forces between molecules of the pure liquids (A-A and ?? - ?? ). 
This stronger attraction makes it harder for molecules to escape into the vapor phase. 
Effect on Vapor Pressure and Boiling Point 
Vapor Pressure : Since the molecules are held more tightly, the vapor pressure of the solution will be 
lower than expected from Raoult's law. Decreased vapor pressure. 
Boiling Point : A lower vapor pressure means you need to increase the temperature further to reach 
atmospheric pressure, where boiling occurs. Therefore, the boiling point of the solution will be higher 
than expected. Increased boiling point. 
Q7:Mass of ethylene glycol (antifreeze) to be added to ???? . ?? ???? of water to protect the freezing point 
at -????
°
?? is ???? (Molar mass in ?? ?????? -?? for ethylene glycol ???? , ?? ?? of water = ?? . ???? ?? ???? ?????? -?? )    
[JEE Main 2024 (Online) 1st February Evening Shift] 
Ans:  15 
To determine the mass of ethylene glycol (antifreeze) needed to lower the freezing point of water to 
-24
°
C, we can use the freezing point depression equation, which is a colligative property given by: 
??? ?? = ?? · ?? ?? · ?? 
where: 
??? ?? is the depression in the freezing point. 
?? is the van't Hoff factor, which is the number of particles the solute splits into in solution. For ethylene 
glycol, which does not dissociate in solution, ?? = 1. 
?? ?? is the cryoscopic constant (freezing point depression constant) of water, which is given as 
Page 5


JEE Mains Previous Year Questions 
(2021-2024): Solutions 
2024 
Q1: We have three aqueous solutions of ???????? labelled as ' ?? ,' ' ?? ' and ' ?? ' with concentration 
?? . ???? , ?? . ?????? and ?? . ???????? , respectively. The value of van ' ?? Hoff factor(i) for these solutions will be 
in the order: 
A. ?? ?? < ?? ?? < ?? ?? 
B. ?? ?? < ?? ?? < ?? ?? 
C. ?? ?? > ?? ?? > ?? ?? 
D. ?? ?? = ?? ?? = ?? ??   [JEE Main 2024 (Online) 1st February Morning Shift] 
Ans: (b) 
 
Salt Values of i (for different conc. of a Salt) 
NaCl 0.1M 0.01M 0.001M 
 1.87 1.94 1.94 
 
The van 't Hoff factor (i) is used to describe the number of particles a solute formula unit produces in a 
solution. For an electrolyte like NaCl, which dissociates completely in very dilute solutions, the 
theoretical value of ?? is approximately 2, since NaCl dissociates into Na
+
and Cl
-
ions. 
In real scenarios, as the concentration of the solution decreases (making the solution more dilute), the 
interaction between the ions decreases, allowing more complete dissociation. Therefore, for practical 
purposes, the van 't Hoff factor ?? approaches its theoretical maximum value as concentration decreases. 
Thus, for NaCl solutions of concentrations 0.1M, 0.01M, and 0.001M, the fact that NaCl dissociates 
more completely in more dilute solutions implies that ?? increases with decreasing concentration. 
Hence, the order of ?? based on the concentration would be i
A
< i
B
< i
C
, as concentration 0.1M >
0.01M > 0.001M, respectively. Thus, option B correctly describes the order of the van 't Hoff factors for 
these solutions. 
Q2: Identify the mixture that shows positive deviations from Raoult's Law 
A. (????
?? )
?? ???? + ????
?? 
B. (????
?? )
?? ???? + ?? ?? ?? ?? ????
?? 
C. ???????? ?? + ?? ?? ?? ?? 
D. ???????? ?? + (????
?? )
?? ????    [JEE Main 2024 (Online) 31st January Morning Shift] 
Ans: (a) 
(CH
3
)
2
CO + CS
2
 Exibits positive deviations from Raoult's Law. 
Q3: Match List I with List II 
 List - 1 (Technique)  List - II (Application 
(A) Distillation (I) 
Separation of glycerol 
from spent-lye 
 
(B) Fractional distillation (II) Aniline - Water mixture 
(C) Steam distillation (iII) 
Separation of crude oil 
fractions 
 
(D) 
Distillation under reduced 
pressure 
 
(?? ) Chloroform - Aniline 
Choose the correct answer from the options given below: 
A. A-I, B-II, C-IV, D-III 
B. A-II, B-III, C-I, D-IV 
C. A-IV, B-I, C-II, D-III 
D. A-IV, B-III, C-II, D-I     [JEE Main 2024 (Online) 31st January Morning Shift] 
Ans: In order to match the techniques listed in List I with their corresponding applications in List II, we 
need to understand what each technique is generally used for: 
Distillation: A process used to separate components in a liquid mixture by selective evaporation and 
condensation. It is used for mixtures where the components have significantly different boiling points. 
Fractional distillation: An advanced form of distillation used when the boiling points of the components 
are closer. It involves the use of a fractionating column, which allows for multiple simple distillations to 
occur within the column, hence separating components with similar boiling points. 
Steam distillation: Used to purify temperature-sensitive materials, like organic compounds, that might 
decompose at higher temperatures. This process allows distillation at temperatures below the 
substances' regular boiling points. 
Distillation under reduced pressure (Vacuum distillation): Used for substances that may decompose or 
react at high temperatures. By reducing the pressure, the boiling points of the components are reduced, 
allowing distillation to proceed at lower temperatures. 
Now applying this knowledge to the applications provided in List II: 
Separation of glycerol from spent-lye: This is typically done by simple distillation since glycerol and 
water (spent-lye) have a sufficiently large difference in boiling points. 
Aniline - Water mixture: Since aniline and water form an azeotrope, they have very similar boiling 
points, and separation would typically require fractional distillation. 
Separation of crude oil fractions: Fractional distillation is used to separate various components of crude 
oil due to the narrow differences in their boiling points. 
Chloroform - Aniline: These compounds have significantly different boiling points, so a simple distillation 
could be used, but since aniline can be heat sensitive, distillation under reduced pressure would be the 
best choice to prevent its decomposition. 
Having established the appropriate method for each application, we can match List I with List II: 
(A) Distillation ? (I) Separation of glycerol from spent-lye 
(B) Fractional distillation ? (III) Separation of crude oil fractions 
(C) Steam distillation ? (II) Aniline - Water mixture 
(D) Distillation under reduced pressure ? (IV) Chloroform - Aniline 
Therefore, the correct option that matches List I (Technique) with the proper application in List II is: 
Option D A-IV, B-III, C-II, D-I 
Q4: The solution from the following with highest depression in freezing point/lowest freezing point is 
A. ?????? ?? of acetic acid dissolved in benzene 
B. ?????? ?? of acetic acid dissolved in water 
C. ?????? ?? of benzoic acid dissolved in benzene 
D. ?????? ?? of glucose dissolved in water    [JEE Main 2024 (Online) 30th January Evening Shift] 
Ans: (b) 
?T
f
 is maximum when i × m is maximum. 
1 m
1
=
180
60
= 3, i = 1 + ?? 
Hence 
?T
f
= (1 + ?? ) · k
f
= 3 × 1.86 = 5.58
°
C(?? << 1) 
2 m
2
=
180
60
= 3, i = 0.5, ?T
f
=
3
2
× k
f
'
= 7.68
°
C 
3 m
3
=
180
122
= 1.48, i = 0.5, ?T
f
=
1.48
2
× k
f
 
'
= 3.8
°
C 
4 m
4
=
180
180
= 1, i = 1, ?T
f
= 1 · k
f
 
'
= 1.86
°
C 
As per NCERT, k
f
 
'
(H
2
O) = 1.86k · kgmol
-1
 
k
f
 
'
( Benzene ) = 5.12k · kgmol
-1
 
Q5: What happens to freezing point of benzene when small quantity of napthalene is added to 
benzene? 
A. Increases 
B. Decreases 
C. Remains unchanged 
D. First decreases and then increases     [JEE Main 2024 (Online) 30th January Morning Shift] 
Ans: (b) 
On addition of naphthalene to benzene there is depression in freezing point of benzene. 
Q6: A solution of two miscible liquids showing negative deviation from Raoult's law will have: 
A. increased vapour pressure, increased boiling point 
B. increased vapour pressure, decreased boiling point 
C. decreased vapour pressure, decreased boiling point 
D. decreased vapour pressure, increased boiling point    [JEE Main 2024 (Online) 27th January Morning 
Shift] 
Ans: (d) 
Negative Deviation from Raoult's Law 
Negative deviation means the intermolecular forces of attraction between the molecules of the two 
liquids (A-B) are stronger than the forces between molecules of the pure liquids (A-A and ?? - ?? ). 
This stronger attraction makes it harder for molecules to escape into the vapor phase. 
Effect on Vapor Pressure and Boiling Point 
Vapor Pressure : Since the molecules are held more tightly, the vapor pressure of the solution will be 
lower than expected from Raoult's law. Decreased vapor pressure. 
Boiling Point : A lower vapor pressure means you need to increase the temperature further to reach 
atmospheric pressure, where boiling occurs. Therefore, the boiling point of the solution will be higher 
than expected. Increased boiling point. 
Q7:Mass of ethylene glycol (antifreeze) to be added to ???? . ?? ???? of water to protect the freezing point 
at -????
°
?? is ???? (Molar mass in ?? ?????? -?? for ethylene glycol ???? , ?? ?? of water = ?? . ???? ?? ???? ?????? -?? )    
[JEE Main 2024 (Online) 1st February Evening Shift] 
Ans:  15 
To determine the mass of ethylene glycol (antifreeze) needed to lower the freezing point of water to 
-24
°
C, we can use the freezing point depression equation, which is a colligative property given by: 
??? ?? = ?? · ?? ?? · ?? 
where: 
??? ?? is the depression in the freezing point. 
?? is the van't Hoff factor, which is the number of particles the solute splits into in solution. For ethylene 
glycol, which does not dissociate in solution, ?? = 1. 
?? ?? is the cryoscopic constant (freezing point depression constant) of water, which is given as 
1.86 K kg mol
-1
. 
?? is the molality of the solution. 
However, molality is defined as the number of moles of solute per kilogram of solvent, so we first need 
to find the molality that corresponds to the desired freezing point depression: 
??? ?? = -24
°
C - (0
°
C) = -24
°
C 
Now, we can solve for ?? : 
?? =
??? ?? ?? · ?? ?? 
Substituting the given values: 
?? =
-24
°
C
1 - 1.86 K kg mol
-1
 
Note that C and K are interchangeable when calculating changes in temperature. Now, we can compute 
the molality: 
?? =
-24
1.86
 
Next, we calculate the molality of the ethylene glycol: 
?? ˜ -12.903 mol kg
-1
 
Keep in mind that molality is always positive, but the negative sign indicates the direction of the 
temperature change. Since we're calculating the amount needed, we can consider it as 12.903 moles per 
kilogram of water. 
Now we calculate the moles of ethylene glycol required for 18.6 kg of water: 
moles of ethylene glycol = ?? · mass of water (in kg ) moles of ethylene glycol = 12.903 mol kg
-1
·
18.6 kg moles of ethylene glycol ˜ 240.0158 mol 
Next, we find the mass of ethylene glycol needed using its molar mass: 
mass of ethylene glycol = moles of ethylene glycol · molar mass of ethylene glycol 
Given the molar mass of ethylene glycol is 62 g mol
-1
, we then convert it to kgmol
-1
 by dividing by 
1000 : molar mass of ethylene glycol = 0.062 kg mol
-1
 
Now we can calculate the mass: 
mass of ethylene glycol = 240.0158 mol · 0.062 kg mol
-1
 mass of ethylene glycol ˜ 14.88098 kg 
Therefore, approximately 14.881 kg of ethylene glycol needs to be added to 18.6 kg of water to lower 
the freezing point to -24
°
C.