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Colligative properties Questions in English

Class 12 Chemistry · Solutions · Colligative properties

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1
EasyMCQ
Equimolar solutions in the same solvent have
A
Same boiling point but different freezing point
B
Same freezing point but different boiling point
C
Same boiling and same freezing points
D
Different boiling and different freezing points

Solution

(C) The elevation in the boiling point $(\Delta T_b = K_b \times m)$ and the depression in the freezing point $(\Delta T_f = K_f \times m)$ are colligative properties.
These properties depend on the molality $(m)$ of the solute particles.
Since the solutions are equimolar (same $m$) and in the same solvent (same $K_b$ and $K_f$),the change in boiling point and freezing point will be identical.
Therefore,equimolar solutions of non-electrolytes in the same solvent exhibit the same boiling point and the same freezing point.
2
EasyMCQ
Which of the following is a colligative property?
A
Osmotic pressure
B
Boiling point
C
Vapour pressure
D
Freezing point

Solution

(A) Colligative properties are those properties of solutions that depend only on the number of solute particles and not on their nature. The four main colligative properties are:
$1$. Relative lowering of vapour pressure
$2$. Elevation in boiling point
$3$. Depression in freezing point
$4$. Osmotic pressure
Therefore,$(A)$ Osmotic pressure is a colligative property.
3
MediumMCQ
The colligative properties of a solution depend on
A
Nature of solute particles present in it
B
Nature of solvent used
C
Number of solute particles present in it
D
Number of moles of solvent only

Solution

(C) Colligative properties are those physical properties of a solution that depend solely on the number of solute particles in a given volume of the solution,rather than their chemical nature.
The four main colligative properties are:
$(i)$ Relative lowering of vapour pressure.
$(ii)$ Elevation in boiling point.
$(iii)$ Depression in freezing point.
$(iv)$ Osmotic pressure.
4
EasyMCQ
Which of the following is not a colligative property?
A
Osmotic pressure
B
Elevation in $B.P.$
C
Vapour pressure
D
Depression in freezing point

Solution

(C) Colligative properties are those properties of solutions that depend only on the number of solute particles and not on their nature.
$A$,$B$,and $D$ are colligative properties.
$C$ Vapour pressure is not a colligative property; however,the relative lowering of vapour pressure is a colligative property.
5
EasyMCQ
Which of the following is not a colligative property?
A
Optical activity
B
Elevation in boiling point
C
Osmotic pressure
D
Lowering of vapour pressure

Solution

(A) Colligative properties are properties that depend solely on the number of solute particles present in the solution,rather than their nature.
The four main colligative properties are:
$1$. Relative lowering of vapour pressure
$2$. Elevation in boiling point
$3$. Depression in freezing point
$4$. Osmotic pressure
Optical activity is a property related to the interaction of chiral molecules with plane-polarized light and does not depend on the number of particles. Therefore,it is not a colligative property.
6
EasyMCQ
Colligative properties of a solution depend upon
A
Nature of both solvent and solute
B
The relative number of solute and solvent particles
C
Nature of solute only
D
Nature of solvent only

Solution

(B) Colligative properties are those properties of solutions that depend on the ratio of the number of solute particles to the number of solvent molecules in a solution,and not on the nature of the chemical species present.
7
EasyMCQ
Which is not a colligative property?
A
Refractive index
B
Lowering of vapour pressure
C
Depression of freezing point
D
Elevation of boiling point

Solution

(A) Colligative properties are those properties of solutions that depend only on the number of solute particles relative to the total number of particles present in the solution,and not on the nature of the solute particles.
The four main colligative properties are:
$1$. Relative lowering of vapour pressure
$2$. Elevation of boiling point
$3$. Depression of freezing point
$4$. Osmotic pressure
Refractive index is a physical property that depends on the nature of the material,not on the number of solute particles.
Therefore,Refractive index is not a colligative property.
8
EasyMCQ
Colligative properties are used for the determination of:
A
Molar Mass
B
Equivalent weight
C
Arrangement of molecules
D
Melting point and boiling point

Solution

(A) Colligative properties are properties of solutions that depend only on the number of solute particles in a given amount of solvent,not on their chemical identity.
These properties include relative lowering of vapor pressure,elevation in boiling point,depression in freezing point,and osmotic pressure.
By measuring these properties experimentally,the molar mass of the solute can be calculated using the respective formulas.
9
EasyMCQ
At low concentrations,the statement that equimolal solutions under a given set of experimental conditions have equal osmotic pressure is true for:
A
All solutions
B
Solutions of non-electrolytes only
C
Solutions of electrolytes only
D
None of these

Solution

(B) The osmotic pressure $(\pi)$ is a colligative property given by the formula $\pi = iCRT$,where $i$ is the van't Hoff factor,$C$ is the molar concentration,$R$ is the gas constant,and $T$ is the temperature.
For equimolal solutions,$C$ is the same.
However,for the osmotic pressure to be equal,the van't Hoff factor $(i)$ must also be the same.
Non-electrolytes have $i = 1$,whereas electrolytes dissociate into ions,resulting in $i > 1$.
Therefore,the statement is true only for non-electrolyte solutions.
10
MediumMCQ
What happens when a non-volatile solute is dissolved in water?
A
Increases the vapour pressure of water
B
Decreases the boiling point of water
C
Decreases the freezing point of water
D
All of the above

Solution

(C) When a non-volatile solute is dissolved in water,the vapour pressure of the solvent decreases due to the presence of solute particles at the surface.
As a result of the decrease in vapour pressure,the boiling point of the solution increases (elevation in boiling point) and the freezing point of the solution decreases (depression in freezing point).
11
EasyMCQ
What is the effect of the addition of sugar on the boiling and freezing points of water?
A
Both boiling point and freezing point increases
B
Both boiling point and freezing point decreases
C
Boiling point increases and freezing point decreases
D
Boiling point decreases and freezing point increases

Solution

(C) The addition of a non-volatile solute like sugar to a solvent like water is a classic example of colligative properties.
According to the principles of colligative properties,the addition of a non-volatile solute leads to an elevation in the boiling point and a depression in the freezing point of the solvent.
Therefore,the boiling point of water increases and the freezing point of water decreases upon the addition of sugar.
12
MediumMCQ
Which one of the following aqueous solutions will exhibit the highest boiling point?
A
$0.015 \ M$ urea
B
$0.01 \ M \ KNO_3$
C
$0.01 \ M \ Na_2SO_4$
D
$0.015 \ M$ glucose

Solution

(C) The elevation in boiling point $(\Delta T_b)$ is a colligative property,which is directly proportional to the van't Hoff factor $(i)$ and the molarity $(M)$ of the solution: $\Delta T_b = i \times K_b \times M$.
For non-electrolytes like urea and glucose,$i = 1$.
For $KNO_3$,$i = 2$ $(K^{+} + NO_3^{-})$.
For $Na_2SO_4$,$i = 3$ $(2Na^{+} + SO_4^{2-})$.
Calculating the effective concentration $(i \times M)$:
$A: 1 \times 0.015 = 0.015 \ M$
$B: 2 \times 0.01 = 0.02 \ M$
$C: 3 \times 0.01 = 0.03 \ M$
$D: 1 \times 0.015 = 0.015 \ M$
Since $0.01 \ M \ Na_2SO_4$ has the highest effective concentration of solute particles,it will exhibit the highest boiling point.
13
EasyMCQ
Which of the following solutions boils at the highest temperature?
A
$0.1 \ M$ glucose
B
$0.1 \ M$ $NaCl$
C
$0.1 \ M$ $BaCl_2$
D
$0.1 \ M$ Urea

Solution

(C) $BaCl_2$ dissociates into $3$ ions $(Ba^{2+} + 2Cl^{-})$,whereas $NaCl$ dissociates into $2$ ions $(Na^{+} + Cl^{-})$.
Glucose and Urea are non-electrolytes $(i = 1)$.
Since boiling point elevation is given by $\Delta T_b = i \cdot K_b \cdot m$,the solution with the highest van't Hoff factor $(i)$ will have the highest boiling point.
Comparing the values of $i$:
For $BaCl_2$,$i = 3$.
For $NaCl$,$i = 2$.
For glucose and urea,$i = 1$.
Therefore,$0.1 \ M$ $BaCl_2$ has the highest boiling point.
14
MediumMCQ
Which of the following has the highest boiling point?
A
$0.1 \, N \, Na_2SO_4$
B
$0.1 \, N \, MgSO_4$
C
$0.1 \, M \, Al_2(SO_4)_3$
D
$0.1 \, M \, BaSO_4$

Solution

(C) The elevation in boiling point is given by $\Delta T_b = i \times K_b \times m$.
Since $K_b$ is constant,$\Delta T_b$ depends on the product of the van't Hoff factor $(i)$ and the molarity $(M)$.
For $0.1 \, N \, Na_2SO_4$,$M = 0.1 / 2 = 0.05 \, M$,so $i \times M = 3 \times 0.05 = 0.15$.
For $0.1 \, N \, MgSO_4$,$M = 0.1 / 2 = 0.05 \, M$,so $i \times M = 2 \times 0.05 = 0.10$.
For $0.1 \, M \, Al_2(SO_4)_3$,$i = 5$,so $i \times M = 5 \times 0.1 = 0.50$.
For $0.1 \, M \, BaSO_4$,$i = 2$ (assuming complete dissociation),so $i \times M = 2 \times 0.1 = 0.20$.
Since $Al_2(SO_4)_3$ has the highest value of $i \times M$,it has the highest boiling point.
15
MediumMCQ
When a non-volatile solute is dissolved in water,which of the following occurs?
A
The vapor pressure of water increases.
B
The boiling point of water decreases.
C
The freezing point of water decreases.
D
All of the above.

Solution

(C) When a non-volatile solute is added to a solvent,it leads to colligative properties.
$1$. Vapor pressure of the solution decreases because solute particles occupy surface area.
$2$. Boiling point of the solution increases (elevation in boiling point).
$3$. Freezing point of the solution decreases (depression in freezing point).
Therefore,only option $C$ is correct.
16
EasyMCQ
What happens to the boiling point and freezing point of water when sugar is added to it?
A
Both boiling point and freezing point increase.
B
Both boiling point and freezing point decrease.
C
Boiling point increases and freezing point decreases.
D
Boiling point decreases and freezing point increases.

Solution

(C) When a non-volatile solute like sugar is added to a solvent like water,it leads to colligative properties.
$1$. Elevation in boiling point: The presence of solute particles decreases the vapor pressure of the solution,requiring a higher temperature to reach the atmospheric pressure,thus the boiling point increases.
$2$. Depression in freezing point: The presence of solute particles interferes with the formation of the solid crystal lattice of the solvent,requiring a lower temperature to freeze,thus the freezing point decreases.
17
MediumMCQ
Equimolar solutions in the same solvent have ...
A
Same freezing point but different boiling point
B
Same boiling point but different freezing point
C
Different boiling and freezing points
D
Same boiling point and freezing point

Solution

(D) Colligative properties like elevation in boiling point $(\Delta T_b)$ and depression in freezing point $(\Delta T_f)$ depend only on the number of solute particles in the solution.
For equimolar solutions (same concentration) in the same solvent,the number of solute particles is the same.
Therefore,the elevation in boiling point and the depression in freezing point will be the same for all such solutions.
Since $\Delta T_b = T_b - T_b^0$ and $\Delta T_f = T_f^0 - T_f$,if $\Delta T_b$ and $\Delta T_f$ are constant,then the boiling point $(T_b)$ and freezing point $(T_f)$ of the solutions will also be the same.
18
EasyMCQ
The colligative property of a solution depends on.....
A
Nature of the solution
B
Nature of the solvent
C
Number of solute particles
D
Number of moles of solvent

Solution

(C) Colligative properties are those properties of solutions that depend only on the number of solute particles present in a given amount of solvent,regardless of their chemical nature. Therefore,the correct option is $C$.
19
EasyMCQ
Which of the following is not a colligative property?
A
Osmotic pressure
B
Lowering of vapour pressure
C
Depression in freezing point
D
Refractive index

Solution

(D) Colligative properties depend only on the number of solute particles in a solution, not on their nature.
$Osmotic \ pressure$, $lowering \ of \ vapour \ pressure$, and $depression \ in \ freezing \ point$ are colligative properties.
$Refractive \ index$ is an optical property and is not a colligative property.
20
EasyMCQ
Which of the following has the highest freezing point?
A
$1 \ M \ NaCl$ solution
B
$1 \ M \ KCl$ solution
C
$1 \ M \ CaCl_2$ solution
D
$1 \ M \ \text{Urea}$ solution

Solution

(D) The depression in freezing point $(\Delta T_f)$ is a colligative property,which depends on the van't Hoff factor $(i)$.
$\Delta T_f = i \times K_f \times m$.
Since the molality $(m)$ is the same for all solutions,the one with the lowest van't Hoff factor $(i)$ will have the smallest depression in freezing point,and thus the highest freezing point.
For $1 \ M \ NaCl$,$i = 2$ $(Na^+ + Cl^-)$.
For $1 \ M \ KCl$,$i = 2$ $(K^+ + Cl^-)$.
For $1 \ M \ CaCl_2$,$i = 3$ $(Ca^{2+} + 2Cl^-)$.
For $1 \ M \ \text{Urea}$,$i = 1$ (non-electrolyte).
Since urea has the lowest $i$ value,it undergoes the least depression in freezing point,resulting in the highest freezing point among the given options.
21
EasyMCQ
Which solution will have the highest boiling point?
A
$1\%$ solution of glucose in water
B
$1\%$ solution of sodium chloride in water
C
$1\%$ solution of zinc sulphate in water
D
$1\%$ solution of urea in water

Solution

(B) The boiling point elevation is a colligative property,which depends on the number of particles (van't Hoff factor,$i$) in the solution.
For $1\%$ solutions,the molarity is approximately the same.
Glucose $(C_6H_{12}O_6)$ and urea $(NH_2CONH_2)$ are non-electrolytes,so $i = 1$.
$NaCl$ dissociates as $NaCl \rightarrow Na^+ + Cl^-$ $(i = 2)$.
$ZnSO_4$ dissociates as $ZnSO_4 \rightarrow Zn^{2+} + SO_4^{2-}$ $(i = 2)$.
Since the molar mass of $NaCl$ $(58.44 \ g/mol)$ is lower than that of $ZnSO_4$ $(161.47 \ g/mol)$,a $1\%$ solution of $NaCl$ contains more moles of solute per unit volume than a $1\%$ solution of $ZnSO_4$.
Therefore,the $1\%$ solution of $NaCl$ has the highest number of particles and the highest boiling point.
22
EasyMCQ
The colligative properties of a solution depend on:
A
The relative number of solute particles present in it
B
The chemical nature of the solute particle present in it
C
The size of the container used
D
None of these

Solution

(A) Colligative properties are those physical properties of a solution that depend solely on the number of solute particles in a given volume of the solution,rather than their chemical nature.
The four main colligative properties are:
$(i)$ Relative lowering of vapour pressure of the solvent.
$(ii)$ Elevation in boiling point of the solvent.
$(iii)$ Depression in freezing point of the solvent.
$(iv)$ Osmotic pressure.
23
EasyMCQ
For an increase in the difference between $P_A^0$ and $P_A$,which of the following occurs?
A
Boiling point and freezing point both increase
B
Boiling point and freezing point both decrease
C
Boiling point increases,freezing point decreases
D
Boiling point decreases,freezing point increases

Solution

(C) The difference between $P_A^0$ and $P_A$ is the lowering of vapor pressure,which is given by $\Delta P = P_A^0 - P_A = P_A^0 X_B$.
An increase in this difference implies an increase in the mole fraction of the solute $(X_B)$,which means the concentration of the solute increases.
According to the colligative properties:
$1$. Elevation in boiling point: $\Delta T_b = K_b \times m$. As the concentration $(m)$ increases,$\Delta T_b$ increases,so the boiling point increases.
$2$. Depression in freezing point: $\Delta T_f = K_f \times m$. As the concentration $(m)$ increases,$\Delta T_f$ increases,which means the freezing point decreases.
24
EasyMCQ
When $CuSO_4$ is added to a solution of ammonia,what happens to the boiling point and freezing point of the solution?
A
Freezing point is lowered
B
Freezing point is raised
C
Boiling point is raised
D
Both $(A)$ and $(C)$

Solution

(B) When $CuSO_4$ is added to an aqueous ammonia solution,it forms a complex ion $[Cu(NH_3)_4]^{2+}$.
This reaction reduces the total number of solute particles in the solution.
According to colligative properties,the depression in freezing point $(\Delta T_f = i \times K_f \times m)$ and elevation in boiling point $(\Delta T_b = i \times K_b \times m)$ are directly proportional to the van 't Hoff factor $(i)$.
Since the number of particles decreases,the van 't Hoff factor $(i)$ decreases.
Consequently,the freezing point of the solution increases (less depression) and the boiling point decreases (less elevation).
25
EasyMCQ
Equimolal solutions of non-electrolytes in the same solvent have:
A
different freezing and different boiling point
B
same boiling but different freezing point
C
same freezing and same boiling point
D
same freezing but different boiling point

Solution

(C) Colligative properties such as elevation in boiling point $(\Delta T_b)$ and depression in freezing point $(\Delta T_f)$ depend on the molality $(m)$ of the solute particles in the solution.
For non-electrolytes,the van't Hoff factor $(i)$ is $1$.
The formulas are $\Delta T_b = K_b \times m$ and $\Delta T_f = K_f \times m$.
Since the solutions are equimolal (same $m$) and the solvent is the same (same $K_b$ and $K_f$),both $\Delta T_b$ and $\Delta T_f$ will be the same.
Therefore,the boiling point $(T_b = T_b^0 + \Delta T_b)$ and freezing point $(T_f = T_f^0 - \Delta T_f)$ will be the same for both solutions.
26
MediumMCQ
Which observation$(s)$ reflect$(s)$ colligative properties?
$(i)$ $A$ $0.5 \ m$ $NaBr$ solution has a higher vapour pressure than a $0.5 \ m$ $BaCl_2$ solution at the same temperature
$(ii)$ Pure water freezes at the higher temperature than pure methanol
$(iii)$ $A$ $0.1 \ m$ $NaOH$ solution freezes at a lower temperature than pure water
Choose the correct answer from the codes given below
A
$(i)$,$(ii)$ and $(iii)$
B
$(i)$ and $(ii)$
C
$(ii)$ and $(iii)$
D
$(i)$ and $(iii)$

Solution

(D) Colligative properties are properties of solutions that depend on the number of solute particles in a given amount of solvent,not on the nature of the solute.
$(i)$ $NaBr$ dissociates into $2$ ions $(Na^+, Br^-)$ and $BaCl_2$ dissociates into $3$ ions $(Ba^{2+}, 2Cl^-)$. Since $BaCl_2$ produces more particles,it lowers the vapour pressure more than $NaBr$. Thus,$NaBr$ has a higher vapour pressure. This is a colligative property.
$(ii)$ The freezing point of a pure substance is a characteristic property of that substance,not a colligative property. Comparing two different pure solvents is not a colligative phenomenon.
$(iii)$ The addition of a non-volatile solute $(NaOH)$ to a solvent (water) causes freezing point depression. This is a classic colligative property.
Therefore,$(i)$ and $(iii)$ are correct.
27
MediumMCQ
Assertion : The water pouch of an instant cold pack for treating athletic injuries breaks when squeezed and $NH_4NO_3$ dissolves,lowering the temperature.
Reason : Addition of a non-volatile solute into a solvent results in the depression of the freezing point of the solvent.
A
If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
B
If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
C
If the Assertion is correct but Reason is incorrect.
D
If both the Assertion and Reason are incorrect.

Solution

(A) The dissolution of $NH_4NO_3$ in water is an endothermic process,which absorbs heat from the surroundings,thereby lowering the temperature of the pack.
This phenomenon is related to the colligative properties of solutions.
The addition of a non-volatile solute to a solvent leads to a decrease in the vapor pressure,which results in the depression of the freezing point of the solvent.
Since the cooling effect in the cold pack is a practical application of the energy changes associated with dissolving solutes and the principles of colligative properties,both statements are correct and the reason explains the underlying principle.
28
Medium
What are colligative properties? Explain.

Solution

(N/A) Colligative properties are those properties of solutions that depend only on the number of solute particles present in the solution,regardless of their chemical nature.
These properties include:
$(i)$ Relative lowering of vapour pressure of the solvent
$(ii)$ Depression of freezing point of the solvent
$(iii)$ Elevation of boiling point of the solvent
$(iv)$ Osmotic pressure of the solution.
29
EasyMCQ
What are colligative properties?
A
Properties that depend on the chemical nature of the solute particles.
B
Properties that depend only on the number of solute particles in a solution.
C
Properties that depend on the mass of the solvent.
D
Properties that are independent of the concentration of the solution.

Solution

(B) Colligative properties are those properties of solutions that depend only on the number of solute particles present in the solution,regardless of their chemical nature or identity.
Examples include relative lowering of vapour pressure,elevation of boiling point,depression of freezing point,and osmotic pressure.
30
DifficultMCQ
Which of the following aqueous solutions will exhibit the highest boiling point?
A
$0.01 \ M$ Urea
B
$0.01 \ M \ KNO_3$
C
$0.01 \ M \ Na_2SO_4$
D
$0.015 \ M \ C_6H_{12}O_6$

Solution

(C) The elevation in boiling point is given by the formula: $\Delta T_b = i \cdot K_b \cdot m$.
Since $K_b$ is constant for the same solvent (water) and assuming molality $m \approx M$,the boiling point depends on the product of the van't Hoff factor $(i)$ and molarity $(M)$.
Calculating $i \times M$ for each:
$A$: Urea is a non-electrolyte,$i = 1$. $1 \times 0.01 = 0.01$.
$B$: $KNO_3 \rightarrow K^+ + NO_3^-$,$i = 2$. $2 \times 0.01 = 0.02$.
$C$: $Na_2SO_4 \rightarrow 2Na^+ + SO_4^{2-}$,$i = 3$. $3 \times 0.01 = 0.03$.
$D$: Glucose $(C_6H_{12}O_6)$ is a non-electrolyte,$i = 1$. $1 \times 0.015 = 0.015$.
Since the product $i \times M$ is highest for $Na_2SO_4$,it will exhibit the highest boiling point.
31
DifficultMCQ
Consider $0.1 \ M$ solutions of two solutes $X$ and $Y$. The solute $X$ behaves as a univalent electrolyte while the solute $Y$ dimerises in solution. Which of the following statements are correct regarding these solutions?
$(a)$ The boiling point of the solution of $X$ will be higher than that of $Y$
$(b)$ The osmotic pressure of the solution of $X$ will be higher than that of $Y$
$(c)$ The freezing point of the solution of $X$ will be lower than that of $Y$
$(d)$ The relative lowering of vapour pressure of both the solutions will be the same
Select the correct answer from the given options $:-$
A
$a, b$ and $c$
B
$b, c$ and $d$
C
$a, b$ and $d$
D
$a, c$ and $d$

Solution

(A) For solute $X$ (univalent electrolyte),the van't Hoff factor $i_X \approx 2$. Thus,the effective concentration is $0.1 \times 2 = 0.2 \ M$.
For solute $Y$ (dimerises),the van't Hoff factor $i_Y \approx 0.5$. Thus,the effective concentration is $0.1 \times 0.5 = 0.05 \ M$.
Since the effective concentration of $X$ is greater than $Y$,colligative properties like boiling point elevation and osmotic pressure will be higher for $X$,and freezing point depression will be greater for $X$ (meaning a lower freezing point).
Relative lowering of vapour pressure depends on the number of particles,which differs for $X$ and $Y$,so statement $(d)$ is incorrect.
Therefore,statements $(a), (b),$ and $(c)$ are correct.
32
EasyMCQ
Which among the following is $NOT$ a colligative property?
A
Vapour pressure lowering
B
Boiling point
C
Freezing point depression
D
Osmotic pressure

Solution

(B) Colligative properties are those properties of solutions that depend only on the number of solute particles present in the solution,not on their nature.
These include:
$1$. Relative lowering of vapour pressure
$2$. Elevation of boiling point
$3$. Depression of freezing point
$4$. Osmotic pressure
Among the given options,$A$,$C$,and $D$ are colligative properties.
$B$ (Boiling point) is a physical property of the solvent/solution,whereas 'Elevation of boiling point' is the colligative property.
Therefore,the correct answer is $B$.
33
EasyMCQ
Which of the following is $NOT$ a colligative property?
A
Freezing point depression.
B
Osmotic pressure.
C
Vapour pressure of pure benzene.
D
Boiling point elevation.

Solution

(C) Colligative properties are properties of solutions that depend on the number of solute particles in a given amount of solvent and not on the nature of the solute particles. The four main colligative properties are:
$1$. Relative lowering of vapour pressure
$2$. Elevation of boiling point
$3$. Depression of freezing point
$4$. Osmotic pressure
Since 'vapour pressure of pure benzene' is a property of the pure solvent and not a property dependent on the number of solute particles,it is $NOT$ a colligative property.
34
EasyMCQ
Which of the following is not a colligative property?
A
Elevation in boiling point
B
Lowering of vapour pressure
C
Osmotic pressure
D
Freezing point

Solution

(D) Colligative properties depend on the number of solute particles in a solution. The four main colligative properties are:
$1$. Relative lowering of vapour pressure
$2$. Elevation in boiling point
$3$. Depression in freezing point
$4$. Osmotic pressure
Since 'Freezing point' is a physical property of a substance and not a colligative property (which is the 'Depression in freezing point'),option $D$ is the correct answer.
35
EasyMCQ
Which of the following aqueous solutions should have the minimum boiling point?
A
$0.1 \ M$ Urea
B
$0.1 \ M \ K_2SO_4$
C
$0.1 \ M \ NaCl$
D
$0.1 \ M \ FeCl_3$

Solution

(A) The elevation in boiling point is a colligative property,which depends on the van't Hoff factor $(i)$ and the concentration of the solute particles. The formula is $\Delta T_b = i \times K_b \times m$.
Since the molality $(m)$ is the same for all solutions $(0.1 \ M)$,the solution with the minimum van't Hoff factor $(i)$ will have the minimum boiling point elevation,and thus the minimum boiling point.
For Urea (non-electrolyte),$i = 1$.
For $K_2SO_4$ $(2K^+ + SO_4^{2-})$,$i = 3$.
For $NaCl$ $(Na^+ + Cl^-)$,$i = 2$.
For $FeCl_3$ $(Fe^{3+} + 3Cl^-)$,$i = 4$.
Comparing the values,Urea has the lowest $i$ value $(1)$,therefore $0.1 \ M$ Urea has the minimum boiling point.
36
EasyMCQ
Which of the following is not a colligative property?
A
Osmotic pressure
B
Optical activity
C
Depression in freezing point
D
Elevation in boiling point

Solution

(B) Colligative properties are properties of solutions that depend only on the number of solute particles present in a given amount of solvent,not on their identity.
Common colligative properties include:
$1$. Relative lowering of vapour pressure
$2$. Elevation in boiling point
$3$. Depression in freezing point
$4$. Osmotic pressure
Optical activity is a property related to the interaction of a substance with plane-polarized light and is not dependent on the number of solute particles.
Therefore,optical activity is not a colligative property.
37
EasyMCQ
Which among the following is a colligative property?
A
Surface tension
B
Osmotic pressure
C
Optical rotation
D
Viscosity

Solution

(B) Colligative properties are those properties of solutions that depend only on the number of solute particles present in the solution,regardless of their chemical nature.
Osmotic pressure $(\Pi)$ is a colligative property because it is directly proportional to the molar concentration of the solute particles,as given by the equation $\Pi = CRT$.
38
MediumMCQ
Match the items given in Column-$I$ (method used for determining colligative property) and Column-$II$ (the corresponding colligative property) and find the correct order.
Column-$I$Column-$II$
$A$. Beckmann method$1$. Osmotic pressure
$B$. Ostwald-Walker method$2$. Elevation in $B$.$P$.
$C$. Berkeley-Hartley method$3$. Depression in $F$.$P$.
$D$. Landsberger method$4$. Relative lowering of vapour pressure
A
$A-2, B-4, C-3, D-1$
B
$A-1, B-4, C-2, D-3$
C
$A-2, B-3, C-4, D-1$
D
$A-3, B-4, C-1, D-2$

Solution

(D) The correct matching of the methods with their respective colligative properties is:
$A$. Beckmann method $\rightarrow$ $3$. Depression in $F$.$P$.
$B$. Ostwald-Walker method $\rightarrow$ $4$. Relative lowering of vapour pressure
$C$. Berkeley-Hartley method $\rightarrow$ $1$. Osmotic pressure
$D$. Landsberger method $\rightarrow$ $2$. Elevation in $B$.$P$.
Therefore,the correct order is $A-3, B-4, C-1, D-2$.

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