Solutions
237 Questions
Start JEE Mains Test
2022
Q101
JEE Mains
Numerical
14 Mar 2026
When a certain amount of solid A is dissolved in $100 \mathrm{~g}$ of water at $25^{\circ} \mathrm{C}$ to make a dilute solution, the vapour pressure of the solution is reduced to one-half of that of pure water. The vapour pressure of pure water is $23.76 \,\mathrm{mmHg}$. The number of moles of solute A added is _____________. (Nearest Integer)
Correct Answer: 6
Explanation:
$\because$ Diliute solution given:
$ \frac{\mathrm{P}^0-\mathrm{P}_{\mathrm{S}}}{\mathrm{P}^0} \sim \frac{{ }^{\mathrm{n}} \text { solute }}{{ }^{\mathrm{n}} \text { solvent }} $
$ \frac{\mathrm{P}^0-\mathrm{P}^0 / 2}{\mathrm{P}^0}=\frac{{ }^{\mathrm{n}} \text { solute }}{{ }^{\mathrm{n}} \text { solvent }} $
${ }^{\mathrm{n}}$ solute $\sim \frac{{ }^{\mathrm{n}} \text { solvent }}{2}=\frac{100}{18 \times 2}=2.78 \mathrm{~mol}$
More accurate approach:
$ \frac{\mathrm{P}^0-\mathrm{P}_{\mathrm{S}}}{\mathrm{P}_{\mathrm{S}}}=\frac{{ }^{\mathrm{n}} \text { solute }}{{ }^{\mathrm{n}} \text { solvent }} $
$ \frac{\mathrm{P}^0-\mathrm{P}^0 / 2}{\mathrm{P}^0 / 2}=\frac{{ }^{\mathrm{n}} \text { solute }}{{ }^n \text { solvent }} $
${ }^n$ solute $={ }^n$ solvent $=\frac{100}{18}=5.55 \mathrm{~mol}$
$ \frac{\mathrm{P}^0-\mathrm{P}_{\mathrm{S}}}{\mathrm{P}^0} \sim \frac{{ }^{\mathrm{n}} \text { solute }}{{ }^{\mathrm{n}} \text { solvent }} $
$ \frac{\mathrm{P}^0-\mathrm{P}^0 / 2}{\mathrm{P}^0}=\frac{{ }^{\mathrm{n}} \text { solute }}{{ }^{\mathrm{n}} \text { solvent }} $
${ }^{\mathrm{n}}$ solute $\sim \frac{{ }^{\mathrm{n}} \text { solvent }}{2}=\frac{100}{18 \times 2}=2.78 \mathrm{~mol}$
More accurate approach:
$ \frac{\mathrm{P}^0-\mathrm{P}_{\mathrm{S}}}{\mathrm{P}_{\mathrm{S}}}=\frac{{ }^{\mathrm{n}} \text { solute }}{{ }^{\mathrm{n}} \text { solvent }} $
$ \frac{\mathrm{P}^0-\mathrm{P}^0 / 2}{\mathrm{P}^0 / 2}=\frac{{ }^{\mathrm{n}} \text { solute }}{{ }^n \text { solvent }} $
${ }^n$ solute $={ }^n$ solvent $=\frac{100}{18}=5.55 \mathrm{~mol}$
2022
Q102
JEE Mains
Numerical
14 Mar 2026
The elevation in boiling point for 1 molal solution of non-volatile solute A is $3 \mathrm{~K}$. The depression in freezing point for 2 molal solution of $\mathrm{A}$ in the same solvent is 6 $K$. The ratio of $K_{b}$ and $K_{f}$ i.e., $K_{b} / K_{f}$ is $1: X$. The value of $X$ is [nearest integer]
Correct Answer: 1
Explanation:
Molality of a solution of non volatile solute $(A)=1$
Elevation in boiling point is given by
$\Delta \mathrm{T}_{\mathrm{b}}=\mathrm{K}_{\mathrm{b}} \mathrm{m}$
$ 3=\mathrm{K}_{\mathrm{b}} \times 1 $ ... (1)
Molality of $(A)$ in the same solvent $=2$
Depression in freezing point is given by
$ \begin{aligned} &\Delta \mathrm{T}_{\mathrm{f}}=\mathrm{K}_{\mathrm{f}} \mathrm{m} \\ &6=\mathrm{K}_{\mathrm{f}} \times 2 \quad\quad\quad{...(2)} \\ &\text { Dividing (1) by (2) } \\ &\frac{\mathrm{K}_{\mathrm{b}}}{\mathrm{K}_{\mathrm{f}}}=\frac{1}{\mathrm{X}}=\frac{1}{1} \\ &\therefore \quad \mathrm{X}=1 \end{aligned} $
Elevation in boiling point is given by
$\Delta \mathrm{T}_{\mathrm{b}}=\mathrm{K}_{\mathrm{b}} \mathrm{m}$
$ 3=\mathrm{K}_{\mathrm{b}} \times 1 $ ... (1)
Molality of $(A)$ in the same solvent $=2$
Depression in freezing point is given by
$ \begin{aligned} &\Delta \mathrm{T}_{\mathrm{f}}=\mathrm{K}_{\mathrm{f}} \mathrm{m} \\ &6=\mathrm{K}_{\mathrm{f}} \times 2 \quad\quad\quad{...(2)} \\ &\text { Dividing (1) by (2) } \\ &\frac{\mathrm{K}_{\mathrm{b}}}{\mathrm{K}_{\mathrm{f}}}=\frac{1}{\mathrm{X}}=\frac{1}{1} \\ &\therefore \quad \mathrm{X}=1 \end{aligned} $
2022
Q103
JEE Mains
Numerical
14 Mar 2026
Elevation in boiling point for 1.5 molal solution of glucose in water is 4 K. The depression in freezing point for 4.5 molal solution of glucose in water is 4 K. The ratio of molal elevation constant to molal depression constant (Kb/Kf) is _________.
Correct Answer: 3
Explanation:
$\begin{aligned}
&\Delta \mathrm{T}_{\mathrm{b}}=\mathrm{iK}_{\mathrm{b}} \mathrm{m} \\\\
&\Delta \mathrm{T}_{\mathrm{f}}=\mathrm{iK}_{\mathrm{f}} \mathrm{m} \\\\
&\frac{4}{4}=\frac{\mathrm{K}_{\mathrm{b}} 1.5}{\mathrm{~K}_{\mathrm{f}} 4.5} \\\\
&\frac{\mathrm{K}_{\mathrm{b}}}{\mathrm{K}_{\mathrm{f}}}=3
\end{aligned}$
2022
Q104
JEE Mains
Numerical
14 Mar 2026
1.2 mL of acetic acid is dissolved in water to make 2.0 L of solution. The depression in freezing point observed for this strength of acid is 0.0198$^\circ$C. The percentage of dissociation of the acid is ___________. (Nearest integer)
[Given : Density of acetic acid is 1.02 g mL$-$1, Molar mass of acetic acid is 60 g mol$-$1, Kf(H2O) = 1.85 K kg mol$-$1]
Correct Answer: 5
Explanation:
$\Delta \mathrm{T}_{\mathrm{b}}=\mathrm{i} \times \mathrm{K}_{\mathrm{b}} \times \mathrm{m}$
Moles of solute $($ acetic acid $)=\frac{1.2 \times 1.02}{60}$
As moles of solute are very less.
So, take molarity and molality the same.
$0.0198=\mathrm{i} \times 1.85 \times \frac{1.2 \times 1.02}{60 \times 2}$
$\mathrm{i}=1.05$
$\alpha=\frac{i-1}{n-1}=\frac{0.05}{1}= 0.05 = 5\text{%}$
Moles of solute $($ acetic acid $)=\frac{1.2 \times 1.02}{60}$
As moles of solute are very less.
So, take molarity and molality the same.
$0.0198=\mathrm{i} \times 1.85 \times \frac{1.2 \times 1.02}{60 \times 2}$
$\mathrm{i}=1.05$
$\alpha=\frac{i-1}{n-1}=\frac{0.05}{1}= 0.05 = 5\text{%}$
2022
Q105
JEE Mains
Numerical
14 Mar 2026
2.5 g of protein containing only glycine (C2H5NO2) is dissolved in water to make 500 mL of solution. The osmotic pressure of this solution at 300 K is found to be 5.03 $\times$ 10$-$3 bar. The total number of glycine units present in the protein is ____________.
(Given : R = 0.083 L bar K$-$1 mol$-$1)
Correct Answer: 330
Explanation:
Since,
$ \pi=\mathrm{icR} \mathrm{T} $
$5.03 \times 10^{-3}=\frac{2.5}{M} \times \frac{1000}{500} \times 0.083 \times 300$
Molar mass of protein $=24751.5 \mathrm{~g} / \mathrm{mol}$
Number of glycine units in protein $=\frac{24751.5}{75}$
$ =330 $
$ \pi=\mathrm{icR} \mathrm{T} $
$5.03 \times 10^{-3}=\frac{2.5}{M} \times \frac{1000}{500} \times 0.083 \times 300$
Molar mass of protein $=24751.5 \mathrm{~g} / \mathrm{mol}$
Number of glycine units in protein $=\frac{24751.5}{75}$
$ =330 $
2022
Q106
JEE Mains
Numerical
14 Mar 2026
The vapour pressures of two volatile liquids A and B at 25$^\circ$C are 50 Torr and 100 Torr, respectively. If the liquid mixture contains 0.3 mole fraction of A, then the mole fraction of liquid B in the vapour phase is ${x \over {17}}$. The value of x is ______________.
Correct Answer: 14
Explanation:
$
\begin{aligned}
&\frac{\mathrm{y}_{\mathrm{B}}}{1-\mathrm{y}_{\mathrm{B}}}=\frac{\mathrm{P}_{\mathrm{B}}^{\mathrm{o}}}{\mathrm{P}_{\mathrm{A}}^{\mathrm{o}}}\left[\frac{\mathrm{X}_{\mathrm{B}}}{1-\mathrm{X}_{\mathrm{B}}}\right] \\\\
&\Rightarrow \frac{\mathrm{y}_{\mathrm{B}}}{1-\mathrm{y}_{\mathrm{B}}}=\frac{100}{50}\left[\frac{0.7}{0.3}\right]=\frac{14}{3} \\\\
&\Rightarrow \mathrm{y}_{\mathrm{B}}=\frac{14}{17}
\end{aligned}
$
2022
Q107
JEE Mains
Numerical
14 Mar 2026
A solution containing 2.5 $\times$ 10$-$3 kg of a solute dissolved in 75 $\times$ 10$-$3 kg of water boils at 373.535 K. The molar mass of the solute is ____________ g mol$-$1. [nearest integer] (Given : Kb(H2O) = 0.52 K kg mol$-$1 and boiling point of water = 373.15 K)
Correct Answer: 45
Explanation:
$W_{\text {solute }}=2.5 \times 10^{-3} \mathrm{~kg}$
$ \begin{aligned} &\mathrm{W}_{\text {solvent }}=75 \times 10^{-3} \mathrm{~kg} \\\\ &\Delta \mathrm{T}_{\mathrm{b}} =373.535-373.15 \\\\ &=0.385 \mathrm{~K} \\\\ &\mathrm{~K}_{\mathrm{b}}\left(\mathrm{H}_{2} \mathrm{O}\right) =0.52 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1} \\\\ &\Delta \mathrm{T}_{\mathrm{b}} =\frac{\mathrm{K}_{\mathrm{b}} \times 10^{3} \times \mathrm{W}_{\text {solute }}}{\mathrm{M}_{\text {solute }} \times \mathrm{W}_{\text {solvent }}} \\\\ &\mathrm{M}_{\text {solute }} =\frac{0.52 \times 10^{3} \times 2.5 \times 10^{-3}}{75 \times 10^{-3} \times 0.385} \\\\ &=45.02 \\\\ & \approx 45 \end{aligned} $
$ \begin{aligned} &\mathrm{W}_{\text {solvent }}=75 \times 10^{-3} \mathrm{~kg} \\\\ &\Delta \mathrm{T}_{\mathrm{b}} =373.535-373.15 \\\\ &=0.385 \mathrm{~K} \\\\ &\mathrm{~K}_{\mathrm{b}}\left(\mathrm{H}_{2} \mathrm{O}\right) =0.52 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1} \\\\ &\Delta \mathrm{T}_{\mathrm{b}} =\frac{\mathrm{K}_{\mathrm{b}} \times 10^{3} \times \mathrm{W}_{\text {solute }}}{\mathrm{M}_{\text {solute }} \times \mathrm{W}_{\text {solvent }}} \\\\ &\mathrm{M}_{\text {solute }} =\frac{0.52 \times 10^{3} \times 2.5 \times 10^{-3}}{75 \times 10^{-3} \times 0.385} \\\\ &=45.02 \\\\ & \approx 45 \end{aligned} $
2022
Q108
JEE Mains
Numerical
14 Mar 2026
2 g of a non-volatile non-electrolyte solute is dissolved in 200 g of two different solvents A and B whose ebullioscopic constants are in the ratio of 1 : 8. The elevation in boiling points of A and B are in the ratio ${x \over y}$ (x : y). The value of y is ______________. (Nearest integer)
Correct Answer: 8
Explanation:
$\Delta T b=k b m$
$ \begin{aligned} &\frac{\left(\Delta T_{b}\right)_{A}}{\left(\Delta T_{b}\right)_{B}}=\frac{\left(k_{b}\right)_{A}}{\left(k_{b}\right)_{B}} \\\\ &=\frac{1}{8}=\frac{x}{y} \\\\ &\therefore y=8 \end{aligned} $
$ \begin{aligned} &\frac{\left(\Delta T_{b}\right)_{A}}{\left(\Delta T_{b}\right)_{B}}=\frac{\left(k_{b}\right)_{A}}{\left(k_{b}\right)_{B}} \\\\ &=\frac{1}{8}=\frac{x}{y} \\\\ &\therefore y=8 \end{aligned} $
2022
Q109
JEE Mains
Numerical
14 Mar 2026
The osmotic pressure exerted by a solution prepared by dissolving 2.0 g of protein of molar mass 60 kg mol$-$1 in 200 mL of water at 27$^\circ$C is ______________ Pa. [integer value]
(use R = 0.083 L bar mol$-$1 K$-$1)
Correct Answer: 415
Explanation:
$\pi=\mathrm{i} C R T \quad(\mathrm{i}=1)$
$\pi=\frac{2 \times 1000}{60 \times 10^{3} \times 200} \times .083 \times 300$
$\pi=0.00415 \mathrm{~atm}$
$\pi=415 \mathrm{~Pa}$
$\pi=\frac{2 \times 1000}{60 \times 10^{3} \times 200} \times .083 \times 300$
$\pi=0.00415 \mathrm{~atm}$
$\pi=415 \mathrm{~Pa}$
2022
Q110
JEE Mains
Numerical
14 Mar 2026
A 0.5 percent solution of potassium chloride was found to freeze at $-$0.24$^\circ$C. The percentage dissociation of potassium chloride is ______________. (Nearest integer)
(Molal depression constant for water is 1.80 K kg mol$-$1 and molar mass of KCl is 74.6 g mol$-$1)
Correct Answer: 98
Explanation:
$\Delta \mathrm{T}_{\mathrm{f}}=\mathrm{iK}_{\mathrm{b}} \mathrm{m}$
$ \begin{aligned} &\mathrm{i}=\frac{0.24 \times 99.5 \times 74.6}{1.80 \times 0.5 \times 1000} \\\\ &=1.98 \\\\ &\alpha=\frac{\mathrm{i}-1}{\mathrm{n}-1}=\frac{0.98}{1}=0.98 = 98 \,\% \end{aligned} $
$ \begin{aligned} &\mathrm{i}=\frac{0.24 \times 99.5 \times 74.6}{1.80 \times 0.5 \times 1000} \\\\ &=1.98 \\\\ &\alpha=\frac{\mathrm{i}-1}{\mathrm{n}-1}=\frac{0.98}{1}=0.98 = 98 \,\% \end{aligned} $
2022
Q111
JEE Mains
Numerical
14 Mar 2026
A company dissolves 'x' amount of CO2 at 298 K in 1 litre of water to prepare soda water. X = __________ $\times$ 10$-$3 g. (nearest integer)
(Given : partial pressure of CO2 at 298 K = 0.835 bar.
Henry's law constant for CO2 at 298 K = 1.67 kbar.
Atomic mass of H, C and O is 1, 12, and 6 g mol$-$1, respectively)
Correct Answer: 1221
Explanation:
According to Henry's law, partial pressure of a gas is given by
$P_{g}=\left(K_{H}\right) X_{g}$
where $X_{g}$ is mole fraction of gas in solution
$0.835=1.67 \times 10^{3}\left(\mathrm{X}_{\mathrm{CO}_{2}}\right)$
$\mathrm{X}_{\mathrm{CO}_{2}}=5 \times 10^{-4}$
Mass of $\mathrm{CO}_{2}$ in $1 \mathrm{~L}$ water $=1221 \times 10^{-3} \mathrm{~g}$
$P_{g}=\left(K_{H}\right) X_{g}$
where $X_{g}$ is mole fraction of gas in solution
$0.835=1.67 \times 10^{3}\left(\mathrm{X}_{\mathrm{CO}_{2}}\right)$
$\mathrm{X}_{\mathrm{CO}_{2}}=5 \times 10^{-4}$
Mass of $\mathrm{CO}_{2}$ in $1 \mathrm{~L}$ water $=1221 \times 10^{-3} \mathrm{~g}$
2022
Q112
JEE Mains
Numerical
14 Mar 2026
The osmotic pressure of blood is 7.47 bar at 300 K. To inject glucose to a patient intravenously, it has to be isotonic with blood. The concentration of glucose solution in gL$-$1 is _____________.
(Molar mass of glucose = 180 g mol$-$1, R = 0.083 L bar K$-$1 mol$-$1) (Nearest integer)
Correct Answer: 54
Explanation:
$7.47=\mathrm{C} \times 0.083 \times 300$
$(\pi=\mathrm{CRT})$
(Where C represents the concentration of glucose solution and $\pi$ represents osmotic pressure)
$\mathrm{C}=\frac{7.47}{0.083 \times 300}\left(\mathrm{~mol} \mathrm{~L}^{-1}\right)$
which in $\mathrm{gm} / \mathrm{L}=\frac{7.47}{0.083 \times 300} \times 180$
$ =54 \mathrm{gm} / \mathrm{l} $
$(\pi=\mathrm{CRT})$
(Where C represents the concentration of glucose solution and $\pi$ represents osmotic pressure)
$\mathrm{C}=\frac{7.47}{0.083 \times 300}\left(\mathrm{~mol} \mathrm{~L}^{-1}\right)$
which in $\mathrm{gm} / \mathrm{L}=\frac{7.47}{0.083 \times 300} \times 180$
$ =54 \mathrm{gm} / \mathrm{l} $
2022
Q113
JEE Advanced
Numerical
14 Mar 2026
An aqueous solution is prepared by dissolving $0.1 \mathrm{~mol}$ of an ionic salt in $1.8 \mathrm{~kg}$ of water at $35^{\circ} \mathrm{C}$. The salt remains $90 \%$ dissociated in the solution. The vapour pressure of the solution is $59.724 \mathrm{~mm}$ of Hg. Vapor pressure of water at $35{ }^{\circ} \mathrm{C}$ is $60.000 \mathrm{~mm}$ of $\mathrm{Hg}$. The number of ions present per formula unit of the ionic salt is _________.
Correct Answer: 5
Explanation:
Vapour pressure of solution $\left(\mathrm{P}_{\mathrm{A}}\right)$
$
=59.724 \mathrm{~mm} \text { of } \mathrm{Hg}
$
Vapour pressure of pure water $\left(\mathrm{P}_{\mathrm{A}}^{\circ}\right)$ $ =60.000 \mathrm{~mm} \text { of } \mathrm{Hg} $
Also, $0.1 \mathrm{~mol}$ of an ionic solid is dissolved in $1.8 \mathrm{~kg}$ of water and salt remains $90 \%$ dissocated in the solution.
So, total number of moles $=0.01+0.09 a$ of non-volatile particles.
Now, mass of water $=1.8 \mathrm{~kg}=1.8 \times 1.8 \times 1000 \mathrm{~g}$
Molar mass of water $=18 \mathrm{~g}$
Moles of water $=\frac{1.8 \times 1000}{18}=100$ moles
Using the colligative property, relative lowering in vapour pressure,
$ \frac{\mathrm{P}_{\mathrm{A}}^{\circ}-\mathrm{P}_{\mathrm{A}}}{\mathrm{P}_{\mathrm{A}}^{\circ}}=x_{\mathrm{A}} $
$ \Rightarrow $ $\frac{60-59.724}{60} =\frac{0.01+0.09 a}{100} $
$ \Rightarrow $ $ \frac{0.276}{60} =\frac{0.01+0.09 a}{100} $
$ \Rightarrow $ $ \frac{27.6}{60} =0.01+0.09 a $
$ \Rightarrow $ $ 0.46 =0.01+0.09 a $
$ \Rightarrow $ $ 0.09 a =0.45 $
$ \Rightarrow $ $ a =\frac{0.45}{0.89} $
$ \Rightarrow $ $ a =5 $
So, the number of ions present per formula unit of the ionic salt is 5 .
Vapour pressure of pure water $\left(\mathrm{P}_{\mathrm{A}}^{\circ}\right)$ $ =60.000 \mathrm{~mm} \text { of } \mathrm{Hg} $
Also, $0.1 \mathrm{~mol}$ of an ionic solid is dissolved in $1.8 \mathrm{~kg}$ of water and salt remains $90 \%$ dissocated in the solution.
So, total number of moles $=0.01+0.09 a$ of non-volatile particles.
Now, mass of water $=1.8 \mathrm{~kg}=1.8 \times 1.8 \times 1000 \mathrm{~g}$
Molar mass of water $=18 \mathrm{~g}$
Moles of water $=\frac{1.8 \times 1000}{18}=100$ moles
Using the colligative property, relative lowering in vapour pressure,
$ \frac{\mathrm{P}_{\mathrm{A}}^{\circ}-\mathrm{P}_{\mathrm{A}}}{\mathrm{P}_{\mathrm{A}}^{\circ}}=x_{\mathrm{A}} $
$ \Rightarrow $ $\frac{60-59.724}{60} =\frac{0.01+0.09 a}{100} $
$ \Rightarrow $ $ \frac{0.276}{60} =\frac{0.01+0.09 a}{100} $
$ \Rightarrow $ $ \frac{27.6}{60} =0.01+0.09 a $
$ \Rightarrow $ $ 0.46 =0.01+0.09 a $
$ \Rightarrow $ $ 0.09 a =0.45 $
$ \Rightarrow $ $ a =\frac{0.45}{0.89} $
$ \Rightarrow $ $ a =5 $
So, the number of ions present per formula unit of the ionic salt is 5 .
2021
Q114
JEE Mains
MCQ
14 Mar 2026
Which one of the following 0.10 M aqueous solutions will exhibit the largest freezing point depression?
A.
hydrazine
B.
glucose
C.
glycine
D.
KHSO4
2021
Q115
JEE Mains
MCQ
14 Mar 2026
Which one of the following 0.06 M aqueous solutions has lowest freezing point?
A.
Al2(SO4)3
B.
C6H12O6
C.
KI
D.
K2SO4
2021
Q116
JEE Mains
Numerical
14 Mar 2026
1.22 g of an organic acid is separately dissolved in 100 g of benzene (Kb = 2.6 K kg mol$-$1) and 100 g of acetone (Kb = 1.7 K kg mol$-$1). The acid is known to dimerize in benzene but remain as a monomer in acetone. The boiling point of the solution in acetone increases by 0.17$^\circ$C. The increase in boiling point of solution in benzene in $^\circ$C is x $\times$ 10$-$2. The value of x is ______________. (Nearest integer) [Atomic mass : C = 12.0, H = 1.0, O =16.0]
Correct Answer: 13
Explanation:
With benzene as solvent
$\Delta$Tb = i Kb m
$\Delta$Tb = ${1 \over 2}$ $\times$ 2.6 $\times$ ${{1.22/{M_w}} \over {100/1000}}$ .... (1)
With Acetone as solvent
$\Delta$Tb = i Kb m
0.17 = 1 $\times$ 1.7 $\times$ ${{1.22/{M_w}} \over {100/1000}}$ ..... (2)
(1) / (2)
${{\Delta {T_b}} \over {0.17}} = {{{1 \over 2} \times 2.6 + {{1.22/{M_w}} \over {100/1000}}} \over {1 \times 1.7 \times {{1.22/{M_w}} \over {100/1000}}}}$
$\Delta$Tb = ${{0.26} \over 2}$
$\Delta$Tb = 13 $\times$ 10$-$2
$\Rightarrow$ x = 13
$\Delta$Tb = i Kb m
$\Delta$Tb = ${1 \over 2}$ $\times$ 2.6 $\times$ ${{1.22/{M_w}} \over {100/1000}}$ .... (1)
With Acetone as solvent
$\Delta$Tb = i Kb m
0.17 = 1 $\times$ 1.7 $\times$ ${{1.22/{M_w}} \over {100/1000}}$ ..... (2)
(1) / (2)
${{\Delta {T_b}} \over {0.17}} = {{{1 \over 2} \times 2.6 + {{1.22/{M_w}} \over {100/1000}}} \over {1 \times 1.7 \times {{1.22/{M_w}} \over {100/1000}}}}$
$\Delta$Tb = ${{0.26} \over 2}$
$\Delta$Tb = 13 $\times$ 10$-$2
$\Rightarrow$ x = 13
2021
Q117
JEE Mains
Numerical
14 Mar 2026
40 g of glucose (Molar mass = 180) is mixed with 200 mL of water. The freezing point of solution is __________ K. (Nearest integer) [Given : Kf = 1.86 K kg mol$-$1; Density of water = 1.00 g cm$-$3; Freezing point of water = 273.15 K]
Correct Answer: 271
Explanation:
Molality = ${{\left( {{{40} \over {180}}} \right)mol} \over {0.2\,Kg}} = \left( {{{10} \over 9}} \right)$ molal
$ \Rightarrow \Delta {T_f} = {T_f} - {T_f}' = 1.86 \times {{10} \over 9}$
$ \Rightarrow {T_f}' = 273.15 - 1.86 \times {{10} \over 9}$
= 271.08 K
$ \simeq $ 271 K (nearest - integer)
$ \Rightarrow \Delta {T_f} = {T_f} - {T_f}' = 1.86 \times {{10} \over 9}$
$ \Rightarrow {T_f}' = 273.15 - 1.86 \times {{10} \over 9}$
= 271.08 K
$ \simeq $ 271 K (nearest - integer)
2021
Q118
JEE Mains
Numerical
14 Mar 2026
1 kg of 0.75 molal aqueous solution of sucrose can be cooled up to $-$4$^\circ$C before freezing. The amount of ice (in g) that will be separated out is __________. (Nearest integer)
[Given : Kf(H2O) = 1.86 K kg mol$-$1]
[Given : Kf(H2O) = 1.86 K kg mol$-$1]
Correct Answer: 518
Explanation:
Let mass of water initially present = x gm
$\Rightarrow$ Mass of sucrose = (1000 $-$ x) gm
$\Rightarrow$ moles of sucrose = $\left( {{{1000 - x} \over {342}}} \right)$
$ \Rightarrow 0.75 = {{\left( {{{1000 - x} \over {342}}} \right)} \over {\left( {{x \over {1000}}} \right)}} \Rightarrow {x \over {1000}} = {{1000 - x} \over {342 \times 0.75}}$
$\Rightarrow$ 256.5x = 106 $-$ 1000x
$\Rightarrow$ x = 795.86 gm
$\Rightarrow$ moles of sucrose = 0.5969
New mass of H2O = a kg
$ \Rightarrow 4 = {{0.5969} \over a} \times 1.86 \Rightarrow $ a = 0.2775 kg
$\Rightarrow$ ice separated = (795.86 $-$ 277.5) = 518.3 gm
$\Rightarrow$ Mass of sucrose = (1000 $-$ x) gm
$\Rightarrow$ moles of sucrose = $\left( {{{1000 - x} \over {342}}} \right)$
$ \Rightarrow 0.75 = {{\left( {{{1000 - x} \over {342}}} \right)} \over {\left( {{x \over {1000}}} \right)}} \Rightarrow {x \over {1000}} = {{1000 - x} \over {342 \times 0.75}}$
$\Rightarrow$ 256.5x = 106 $-$ 1000x
$\Rightarrow$ x = 795.86 gm
$\Rightarrow$ moles of sucrose = 0.5969
New mass of H2O = a kg
$ \Rightarrow 4 = {{0.5969} \over a} \times 1.86 \Rightarrow $ a = 0.2775 kg
$\Rightarrow$ ice separated = (795.86 $-$ 277.5) = 518.3 gm
2021
Q119
JEE Mains
Numerical
14 Mar 2026
83 g of ethylene glycol dissolved in 625 g of water. The freezing point of the solution is ____________ K. (Nearest integer)
[Use : Molal Freezing point depression constant of water = 1.86 K kg mol$-$1]
Freezing Point of water = 273 K
Atomic masses : C : 12.0 u, O : 16.0 u, H : 1.0 u]
[Use : Molal Freezing point depression constant of water = 1.86 K kg mol$-$1]
Freezing Point of water = 273 K
Atomic masses : C : 12.0 u, O : 16.0 u, H : 1.0 u]
Correct Answer: 269
Explanation:
kf = 1.86 kg/mol
T$_f^o$ = 273 K
solvent : H2O(625 g)
Solute : 83 g of ethylene glycol
$\Rightarrow$ $\Delta$Tf = kf $\times$ m
$\Rightarrow$ $\left( {T_f^o - T_f^1} \right) = 1.86 \times {{83/62} \over {625/1000}}$
$ \Rightarrow 273 - T_f^1 = {{1.86 \times 83 \times 1000} \over {62 \times 625}} = {{154380} \over {38750}}$
$ \Rightarrow 273 - T_f^1 = 4$
$ \Rightarrow T_f^1 = 259$ K
T$_f^o$ = 273 K
solvent : H2O(625 g)
Solute : 83 g of ethylene glycol
$\Rightarrow$ $\Delta$Tf = kf $\times$ m
$\Rightarrow$ $\left( {T_f^o - T_f^1} \right) = 1.86 \times {{83/62} \over {625/1000}}$
$ \Rightarrow 273 - T_f^1 = {{1.86 \times 83 \times 1000} \over {62 \times 625}} = {{154380} \over {38750}}$
$ \Rightarrow 273 - T_f^1 = 4$
$ \Rightarrow T_f^1 = 259$ K
2021
Q120
JEE Mains
Numerical
14 Mar 2026
Of the following four aqueous solutions, total number of those solutions whose freezing point is lower than that of 0.10 M C2H5OH is __________ (Integer answer)
(i) 0.10 M Ba3(PO4)2
(ii) 0.10 M Na2SO4
(iii) 0.10 M KCl
(iv) 0.10 M Li3PO4
(i) 0.10 M Ba3(PO4)2
(ii) 0.10 M Na2SO4
(iii) 0.10 M KCl
(iv) 0.10 M Li3PO4
Correct Answer: 4
Explanation:
As 0.1 M C2H5OH is non-dissociative and rest all salt given are electrolyte so in each case effective molarity > 0.1 so each will have lower freezing point.
2021
Q121
JEE Mains
Numerical
14 Mar 2026
In a solvent 50% of an acid HA dimerizes and the rest dissociates. The van't Hoff factor of the acid is __________ $\times$ 10$-$2.
(Round off to the nearest integer)
(Round off to the nearest integer)
Correct Answer: 125
Explanation:
Now, $i = {{final\,moles} \over {initial\,moles}} = {{0.25a + 0.5a + 0.5a} \over {0.5a + 0.5a}}$
= 1.25 = 125 $\times$ 10$-$2
2021
Q122
JEE Mains
Numerical
14 Mar 2026
1.46 g of a biopolymer dissolved in a 100 mL water at 300 K exerted an osmotic pressure of 2.42 $\times$ 10$-$3 bar.
The molar mass of the biopolymer is _____________ $\times$ 104 g mol$-$1. (Round off to the Nearest Integer)
[Use : R = 0.083 L bar mol$-$1 K$-$1]
The molar mass of the biopolymer is _____________ $\times$ 104 g mol$-$1. (Round off to the Nearest Integer)
[Use : R = 0.083 L bar mol$-$1 K$-$1]
Correct Answer: 15
Explanation:
$\pi$ = CRT;
$\pi$ = osmotic pressure
C = molarity
T = Temperature of solution
let the molar mass be M gm/mol
2.42 $\times$ 10$-$3 bar = ${{\left( {{{1.46g} \over {Mgm/mol}}} \right)} \over {0.1l}} \times \left( {{{0.083l - bar} \over {mol - K}}} \right) \times (300K)$
$\Rightarrow$ M = 15.02 $\times$ 104 g/mol
$\pi$ = osmotic pressure
C = molarity
T = Temperature of solution
let the molar mass be M gm/mol
2.42 $\times$ 10$-$3 bar = ${{\left( {{{1.46g} \over {Mgm/mol}}} \right)} \over {0.1l}} \times \left( {{{0.083l - bar} \over {mol - K}}} \right) \times (300K)$
$\Rightarrow$ M = 15.02 $\times$ 104 g/mol
2021
Q123
JEE Mains
Numerical
14 Mar 2026
When 3.00 g of a substance 'X' is dissolved in 100 g of CCl4, it raises the boiling point by 0.60 K. The molar mass of the substance 'X' is ______________ g mol$-$1. (Nearest integer).
[Given Kb for CCl4 is 5.0 K kg mol$-$1]
[Given Kb for CCl4 is 5.0 K kg mol$-$1]
Correct Answer: 250
Explanation:
$\Delta$Tb = Kb $\times$ molality
0.60 = 5 $\times$ $\left( {{{3/M} \over {100/100}}} \right)$
M = 250
0.60 = 5 $\times$ $\left( {{{3/M} \over {100/100}}} \right)$
M = 250
2021
Q124
JEE Mains
Numerical
14 Mar 2026
CO2 gas is bubbled through water during a soft drink manufacturing process at 298 K. If CO2 exerts a partial pressure of 0.835 bar then x m mol of CO2 would dissolve in 0.9 L of water. The value of x is ____________. (Nearest integer)
(Henry's law constant for CO2 at 298 K is 1.67 $\times$ 103 bar)
(Henry's law constant for CO2 at 298 K is 1.67 $\times$ 103 bar)
Correct Answer: 25
Explanation:
From Henry's law
Pgas = KH.Xgas
0.835 = 1.67 $\times$ 103 $\times$ ${{n(C{O_2})} \over {{{0.9 \times 1000} \over {18}}}}$
$ \Rightarrow $ n(CO2) = 0.025
Millimoles of CO2 = 0.025 $\times$ 1000 = 25
Pgas = KH.Xgas
0.835 = 1.67 $\times$ 103 $\times$ ${{n(C{O_2})} \over {{{0.9 \times 1000} \over {18}}}}$
$ \Rightarrow $ n(CO2) = 0.025
Millimoles of CO2 = 0.025 $\times$ 1000 = 25
2021
Q125
JEE Mains
Numerical
14 Mar 2026
The vapour pressures of A and B at 25$^\circ$C are 90 mm Hg and 15 mm Hg respectively. If A and B are mixed such that the mole fraction of A in the mixture is 0.6, then the mole fraction of B in the vapour phase is x $\times$ 10$-$1. The value of x is ___________. (Nearest integer)
Correct Answer: 1
Explanation:
xA = 0.6
PT = xAPAo + xBPBo
= 0.6 $\times$ 90 + 0.4 $\times$ 15
= 54 + 6 = 60
xAPAo = yAPT
0.6 $\times$ 90 = yA(60)
$\Rightarrow$ yA = 0.9
yB = 0.1 = 1 $\times$ 10$-$1
$\therefore$ x = 1
PT = xAPAo + xBPBo
= 0.6 $\times$ 90 + 0.4 $\times$ 15
= 54 + 6 = 60
xAPAo = yAPT
0.6 $\times$ 90 = yA(60)
$\Rightarrow$ yA = 0.9
yB = 0.1 = 1 $\times$ 10$-$1
$\therefore$ x = 1
2021
Q126
JEE Mains
Numerical
14 Mar 2026
At 20$^\circ$ C, the vapour pressure of benzene is 70 torr and that of methyl benzene is 20 torr. The mole fraction of benzene in the vapour phase at 20$^\circ$ above an equimolar mixture of benzene and methyl benzene is _____________ $\times$ 10$-$2. (Nearest integer)
Correct Answer: 78
Explanation:
Vapour pressure of pure benzene, $p_A^o$ = 70 Torr
Vapour pressure of pure methyl benzene, $p_B^o$ = 20 Torr
This mixture is equimolar, so number of moles of benzene,
nA = number of moles of methyl benzene, nB
Mole fraction of benzene in vapour phase, yA = ${{{p_A}} \over {{p_T}}}$ .... (i)
where pA is pressure of benzene in mixture.
${p_A} = \mathop {p_A^o{\chi _A}}\limits_{Mole\,fraction} = p_A^o \times {{{n_A}} \over {{n_A} + {n_B}}} = p_A^o \times {{{n \over A}} \over {2{n \over A}}} = {{p_A^o} \over 2}$
pT is total pressure,
${p_T} = p_A^o{\chi _A} + p_B^o{\chi _B} = {p_A} + {p_B}$ (pressure of methyl benzene)
${p_T} = {{p_A^o} \over 2} + {{p_B^o} \over 2} = {{p_A^o + p_B^o} \over 2}$
Putting in above equation (i),
${y_A} = {{{{70} \over 2}} \over {{{(70 + 20)} \over 2}}} = {{70} \over {90}}$
yA = 0.78 = 78 $\times$ 10$-$2
Vapour pressure of pure methyl benzene, $p_B^o$ = 20 Torr
This mixture is equimolar, so number of moles of benzene,
nA = number of moles of methyl benzene, nB
Mole fraction of benzene in vapour phase, yA = ${{{p_A}} \over {{p_T}}}$ .... (i)
where pA is pressure of benzene in mixture.
${p_A} = \mathop {p_A^o{\chi _A}}\limits_{Mole\,fraction} = p_A^o \times {{{n_A}} \over {{n_A} + {n_B}}} = p_A^o \times {{{n \over A}} \over {2{n \over A}}} = {{p_A^o} \over 2}$
pT is total pressure,
${p_T} = p_A^o{\chi _A} + p_B^o{\chi _B} = {p_A} + {p_B}$ (pressure of methyl benzene)
${p_T} = {{p_A^o} \over 2} + {{p_B^o} \over 2} = {{p_A^o + p_B^o} \over 2}$
Putting in above equation (i),
${y_A} = {{{{70} \over 2}} \over {{{(70 + 20)} \over 2}}} = {{70} \over {90}}$
yA = 0.78 = 78 $\times$ 10$-$2
2021
Q127
JEE Mains
Numerical
14 Mar 2026
A solute A dimerizes in water. The boiling point of a 2 molal solution of A is 100.52$^\circ$C. The percentage association of A is __________. (Round off to the Nearest Integer).
[Use : Kb for water = 0.52 K kg mol$-$1 Boiling point of water = 100$^\circ$C]
[Use : Kb for water = 0.52 K kg mol$-$1 Boiling point of water = 100$^\circ$C]
Correct Answer: 100
Explanation:
$\Delta$Tb = Boiling point of the solution $-$ Boiling point of the pure solvent
= 100.52 $-$ 100
= 0.52
$ \therefore $ $\Delta$Tb = Kb (iM)
$ \Rightarrow $ 0.52 = i $\times$ 0.52 $\times$ 2
$ \Rightarrow $ i = ${1 \over 2}$
We know,
i = 1 + $\left( {{1 \over n} - 1} \right)\beta $
here, $\beta$ = degree of dimerization
n = number of particle associated
n = 2 for dimerization
$ \therefore $ ${1 \over 2} = 1 + \left( {{1 \over 2} - 1} \right)\beta $
$ \Rightarrow \beta = 1$
$ \therefore $ % association = 100
= 100.52 $-$ 100
= 0.52
$ \therefore $ $\Delta$Tb = Kb (iM)
$ \Rightarrow $ 0.52 = i $\times$ 0.52 $\times$ 2
$ \Rightarrow $ i = ${1 \over 2}$
We know,
i = 1 + $\left( {{1 \over n} - 1} \right)\beta $
here, $\beta$ = degree of dimerization
n = number of particle associated
n = 2 for dimerization
$ \therefore $ ${1 \over 2} = 1 + \left( {{1 \over 2} - 1} \right)\beta $
$ \Rightarrow \beta = 1$
$ \therefore $ % association = 100
2021
Q128
JEE Mains
Numerical
14 Mar 2026
2 molal solution of a weak acid HA has a freezing point of 3.885$^\circ$C. The degree of dissociation of this acid is ___________ $\times$ 10$-$3. (Round off to the Nearest Integer).
[Given : Molal depression constant of water = 1.85 K kg mol$-$1 Freezing point of pure water = 0$^\circ$ C]
[Given : Molal depression constant of water = 1.85 K kg mol$-$1 Freezing point of pure water = 0$^\circ$ C]
Correct Answer: 50
Explanation:
$\Delta$Tf = Kf (im)
$ \Rightarrow $ 3.885 = i $\times$ 1.85 $\times$ 2
$ \Rightarrow $ i = 1.05
Also, we know,
i = 1 + (n $-$ 1) $\alpha$
here n = number of particle obtained upon the dissociation of one particle.
$HA\rightleftharpoons H^{+}+A^{-} $
here from one particle HA we get two particle H+ and A$-$.
$ \therefore $ n = 2
So, i = 1 + (2 $-$ 1)$\alpha$
$ \Rightarrow $ 1.05 = 1 + $\alpha$
$ \Rightarrow $ $\alpha$ = 0.05 = 50 $\times$ 10$-$3
$ \Rightarrow $ 3.885 = i $\times$ 1.85 $\times$ 2
$ \Rightarrow $ i = 1.05
Also, we know,
i = 1 + (n $-$ 1) $\alpha$
here n = number of particle obtained upon the dissociation of one particle.
$HA\rightleftharpoons H^{+}+A^{-} $
here from one particle HA we get two particle H+ and A$-$.
$ \therefore $ n = 2
So, i = 1 + (2 $-$ 1)$\alpha$
$ \Rightarrow $ 1.05 = 1 + $\alpha$
$ \Rightarrow $ $\alpha$ = 0.05 = 50 $\times$ 10$-$3
2021
Q129
JEE Mains
Numerical
14 Mar 2026
A 1 molal K4Fe(CN)6 solution has a degree of dissociation of 0.4. Its boiling point is equal to that of another solution which contains 18.1 weight percent of a non electrolytic solute A. The molar mass of A is __________ u. (Round off to the Nearest Integer). [Density of water = 1.0 g cm$-$3 ]
Correct Answer: 85
Explanation:
Effective molality = 0.6 + 1.6 + 0.4 = 2.6 m
As elevation in boiling point is a colligative property which depends on the amount of solute. So, to have same boiling point, the molality of two solutions should be same.
Molality of non-electrolyte solution = molality of ${K_4}[Fe{(CN)_6}]$ = 2.6 m
Now, 18.1 weight per cent solution means 18.1 g solute is present in 100 g solution and hence, (100 $-$ 18.1) = 81.9 g water.
$Molality = {{(Mass\,of\,solute/Molar\,mass\,of\,solute)} \over {Mass\,of\,solvent\,in\,kg}} \times 1000$
Now, $2.6 = {{18.1/M} \over {81.9/1000}}$
where, M is the molar mass of non-electrolyte solute
Molar mass of solute, M = 85
2021
Q130
JEE Mains
Numerical
14 Mar 2026
The oxygen dissolved in water exerts a partial pressure of 20 kPa in the vapour above water. The molar solubility of oxygen in water is __________ $\times$ 10$-$5 mol dm$-$3. (Round off to the Nearest Integer).
[Given : Henry's law constant = KH = 8.0 $\times$ 104 kPa for O2. Density of water with dissolved oxygen = 1.0 kg dm$-$3 ]
[Given : Henry's law constant = KH = 8.0 $\times$ 104 kPa for O2. Density of water with dissolved oxygen = 1.0 kg dm$-$3 ]
Correct Answer: 25
Explanation:
The oxygen dissolved in water has a partial pressure of 20 kPa in the vapor phase above the water. To find the molar solubility of oxygen in water, we use Henry's Law, which states:
$ \text{Partial pressure} (P_g) \propto \text{Solubility} $
This can be mathematically expressed as:
$ P_g = K_H \times \text{Solubility} $
Where:
$ P_g $ is the partial pressure of oxygen, given as 20 kPa.
$ K_H $ is Henry's law constant for $ \text{O}_2 $, provided as $ 8.0 \times 10^4 \, \text{kPa} $.
Substituting the given values into the equation:
$ 20 \times 10^3 = (8.0 \times 10^4) \times \text{Solubility} $
Solving for solubility:
$ \text{Solubility} = \frac{20 \times 10^3}{8.0 \times 10^4} $
$ \text{Solubility} = 0.25 \times 10^{-1} $
$ \text{Solubility} = 25 \times 10^{-5} \, \text{mol dm}^{-3} $
Thus, the molar solubility of oxygen in water rounds to 25 × 10-5 mol dm-3.
2021
Q131
JEE Mains
Numerical
14 Mar 2026
At 363 K, the vapour pressure of A is 21 kPa and that of B is 18 kPa. One mole of A and 2 moles of B are mixed. Assuming that this solution is ideal, the vapour pressure of the mixture is ___________ kPa. (Round off to the Nearest Integer).
Correct Answer: 19
Explanation:
${X_A} = {1 \over {1 + 2}} = {1 \over 3}$
${X_B} = {2 \over 3}$
$P_A^o = 21kPa$
$P_B^o = 18kPa$
${P_{total}} = P_A^o{X_A} + P_B^o{X_B}$
$ = 21 \times {1 \over 3} + 18 \times {2 \over 3}$
$ = 7 + 12$
$ = 19 kPa$
${X_B} = {2 \over 3}$
$P_A^o = 21kPa$
$P_B^o = 18kPa$
${P_{total}} = P_A^o{X_A} + P_B^o{X_B}$
$ = 21 \times {1 \over 3} + 18 \times {2 \over 3}$
$ = 7 + 12$
$ = 19 kPa$
2021
Q132
JEE Mains
Numerical
14 Mar 2026
AB2 is 10% dissociated in water to A2+ and B$-$. The boiling point of a 10.0 molal aqueous solution of AB2 is __________$^\circ$C. (Round off to the Nearest Integer).
[Given : Molal elevation constant of water Kb = 0.5 K kg mol$-$1 boiling point of pure water = 100$^\circ$C]
[Given : Molal elevation constant of water Kb = 0.5 K kg mol$-$1 boiling point of pure water = 100$^\circ$C]
Correct Answer: 106
Explanation:
AB2 $ \leftrightharpoons $ A+ + 2B$-$
$ \therefore $ For AB2, n = 3
i = 1 + (n $-$ 1)$\alpha$
= 1 + (3 $-$ 1) $\times$ 0.1
= 1.2
Now, $\Delta$Tb = Kb (im)
$ \Rightarrow $ Tb $-$ T$_b^o$ = 1.2 $\times$ 0.5 $\times$ 10
$ \Rightarrow $ Tb $-$ 100 = 6
$ \Rightarrow $ Tb = 106
$ \therefore $ For AB2, n = 3
i = 1 + (n $-$ 1)$\alpha$
= 1 + (3 $-$ 1) $\times$ 0.1
= 1.2
Now, $\Delta$Tb = Kb (im)
$ \Rightarrow $ Tb $-$ T$_b^o$ = 1.2 $\times$ 0.5 $\times$ 10
$ \Rightarrow $ Tb $-$ 100 = 6
$ \Rightarrow $ Tb = 106
2021
Q133
JEE Mains
Numerical
14 Mar 2026
When 12.2 g of benzoic acid is dissolved in 100 g of water, the freezing point of solution was found to be $-$0.93$^\circ$C (Kf(H2O) = 1.86 K kg mol$-$1). The number (n) of benzoic acid molecules associated (assuming 100% association) is ___________.
Correct Answer: 2
Explanation:
$\underset{\text{Benzoic acid}}{n \mathrm{PhCOOH}} \stackrel{\text { Association }}{\longrightarrow}(\mathrm{PhCOOH})_n$
Assuming $100 \%$ association ( $\alpha=1$ ),
$ \Rightarrow i=1-\alpha\left(1-\frac{1}{n}\right)=\frac{1}{n}[\because \alpha+1] $
Now, $\Delta T_f=K_f \times m \times i$
$ 0-(0.93)=1.86 \times \frac{w_B \times 1000}{w_A \times M_B} \times \frac{1}{n} $
$\left[\because w_B=\right.$ mass of $\mathrm{PhCOOH}=12.2 \mathrm{~g}$
$w_A=$ mass of $\mathrm{H}_2 \mathrm{O}=100 \mathrm{~g}$
$M_B=$ molar mass of $\left.\mathrm{PhCOOH}\right]$
$=122 \mathrm{~g} \mathrm{~mol}^{-1}$
$=1.86 \times \frac{12.2 \times 1000}{100 \times 122} \times \frac{1}{n}$
$ \begin{aligned} \Rightarrow n &=\frac{1.86 \times 12.2 \times 1000}{0.93 \times 100 \times 122}=2 \end{aligned} $
$\therefore$ Number of benzoic acid molecules associated, $n=2$
Assuming $100 \%$ association ( $\alpha=1$ ),
$ \Rightarrow i=1-\alpha\left(1-\frac{1}{n}\right)=\frac{1}{n}[\because \alpha+1] $
Now, $\Delta T_f=K_f \times m \times i$
$ 0-(0.93)=1.86 \times \frac{w_B \times 1000}{w_A \times M_B} \times \frac{1}{n} $
$\left[\because w_B=\right.$ mass of $\mathrm{PhCOOH}=12.2 \mathrm{~g}$
$w_A=$ mass of $\mathrm{H}_2 \mathrm{O}=100 \mathrm{~g}$
$M_B=$ molar mass of $\left.\mathrm{PhCOOH}\right]$
$=122 \mathrm{~g} \mathrm{~mol}^{-1}$
$=1.86 \times \frac{12.2 \times 1000}{100 \times 122} \times \frac{1}{n}$
$ \begin{aligned} \Rightarrow n &=\frac{1.86 \times 12.2 \times 1000}{0.93 \times 100 \times 122}=2 \end{aligned} $
$\therefore$ Number of benzoic acid molecules associated, $n=2$
2021
Q134
JEE Mains
Numerical
14 Mar 2026
224 mL of SO2(g) at 298 K and 1 atm is passed through 100 mL of 0.1 M NaOH solution. The non-volatile solute produced is dissolved in 36g of water. The lowering of vapour pressure of solution (assuming the solution in dilute) (P$_{({H_2}O)}^o$ $-$ 24 mm of Hg) is x $\times$ 10$-$2 mm of Hg, the value of x is ___________. (Integer answer)
Correct Answer: 18TO24
Explanation:
moles of SO2 = ${{224} \over {22400}}$ = 0.01
moles of NaOH = molarity × volume (in litre)
= 0.1 × 0.1
= 0.01 moles
The balanced equation is
SO2 + 2NaOH $ \to $ Na2SO3 + H2O
$ \therefore $ Here NaOH is limiting Reagent.
2 mole NaOH produces 1 mole Na2SO3
0.01 mole NaOH produces ${1 \over 2}$ $ \times $ 0.01 mole Na2SO3
$ \therefore $ Moles of Na2SO3 = 0.005 mole
Na2SO3 $ \to $ 2Na+ + SO32-
van’t Hoff factor (i) = 3
Moles of H2O = ${{36} \over {18}}$ = 2 moles
Accoding to Relative Lowering of Vapour :
${{P_{{H_2}O}^o - {P_S}} \over {P_{{H_2}O}^o}} = {{i{n_{N{a_2}C{O_3}}}} \over {{n_{{H_2}O}} + i{n_{N{a_2}C{O_3}}}}}$
[ ${{n_{N{a_2}C{O_3}}}}$ << ${{n_{{H_2}O}}}$ ]
${{P_{{H_2}O}^o - {P_S}} \over {P_{{H_2}O}^o}} = {{i{n_{N{a_2}C{O_3}}}} \over {{n_{{H_2}O}}}}$
$ \Rightarrow $ ${{24 - {P_S}} \over {24}} = {{3 \times 0.005} \over 2}$
$ \Rightarrow $ 24 – PS = 0.18
$ \Rightarrow $ PS = 23.82
Lowering in pressure ($\Delta $P) = 0.18 mm of Hg
= 18 × 10–2 mm of Hg
moles of NaOH = molarity × volume (in litre)
= 0.1 × 0.1
= 0.01 moles
The balanced equation is
SO2 + 2NaOH $ \to $ Na2SO3 + H2O
$ \therefore $ Here NaOH is limiting Reagent.
2 mole NaOH produces 1 mole Na2SO3
0.01 mole NaOH produces ${1 \over 2}$ $ \times $ 0.01 mole Na2SO3
$ \therefore $ Moles of Na2SO3 = 0.005 mole
Na2SO3 $ \to $ 2Na+ + SO32-
van’t Hoff factor (i) = 3
Moles of H2O = ${{36} \over {18}}$ = 2 moles
Accoding to Relative Lowering of Vapour :
${{P_{{H_2}O}^o - {P_S}} \over {P_{{H_2}O}^o}} = {{i{n_{N{a_2}C{O_3}}}} \over {{n_{{H_2}O}} + i{n_{N{a_2}C{O_3}}}}}$
[ ${{n_{N{a_2}C{O_3}}}}$ << ${{n_{{H_2}O}}}$ ]
${{P_{{H_2}O}^o - {P_S}} \over {P_{{H_2}O}^o}} = {{i{n_{N{a_2}C{O_3}}}} \over {{n_{{H_2}O}}}}$
$ \Rightarrow $ ${{24 - {P_S}} \over {24}} = {{3 \times 0.005} \over 2}$
$ \Rightarrow $ 24 – PS = 0.18
$ \Rightarrow $ PS = 23.82
Lowering in pressure ($\Delta $P) = 0.18 mm of Hg
= 18 × 10–2 mm of Hg
2021
Q135
JEE Mains
Numerical
14 Mar 2026
If a compound AB dissociates to the extent of 75% in an aqueous solution, the molality of the solution which shows a 2.5 K rise in the boiling point of the solution is ____________ molal. (Rounded off to the nearest integer)
[Kb = 0.52 K kg mol$-$1]
[Kb = 0.52 K kg mol$-$1]
Correct Answer: 3
Explanation:
As AB is a binary electrolyte,
$\therefore$ AB $\rightleftharpoons$ A+ + B$-$, n = 2
$i = 1 + \alpha (n - 1) = 1 + {{75} \over {100}}(2 - 1) = 1.75$
Given, $\Delta$Tb = 2.5 K
Kb = 0.52 K kg mol$-$1
$\therefore$ $\Delta$Tb = Kb $\times$ m $\times$ i
$ \Rightarrow m = {{\Delta {T_b}} \over {{K_b} \times i}} = {{2.5} \over {0.52 \times 1.75}}$
$ = 2.74 \simeq 3$ mol/kg
2021
Q136
JEE Mains
Numerical
14 Mar 2026
1 molal aqueous solution of an electrolyte A2B3 is 60% ionised. The boiling point of the solution at 1 atm is _________ K. (Rounded off to the nearest integer)
[Given Kb for (H2O) = 0.52 K kg mol$-$1]
[Given Kb for (H2O) = 0.52 K kg mol$-$1]
Correct Answer: 375
Explanation:
${A_2}{B_3}\buildrel {} \over
\longrightarrow 2{A^{ + 3}} + 3{B^{ - 2}}$
No. of ions = 2 + 3 = 5
i = 1 + (n $-$ 1) $\alpha $
= 1 + (5 $-$ 1) $\times$ 0.6
= 1 + 4 $\times$ 0.6 = 1 + 2.4 = 3.4
$\Delta {T_b} = {K_b} \times m \times i = 0.52 \times 1 \times 3.4 = 1.768^\circ $ C
$\Delta {T_b} = {({T_b})_{solution}} - {[{({T_b})_{{H_2}O}}]_{Solution}}$
$1.768 = {({T_b})_{solution}} - 100$
${({T_b})_{solution}} = 101.768^\circ $ C
$ = 375$ K
No. of ions = 2 + 3 = 5
i = 1 + (n $-$ 1) $\alpha $
= 1 + (5 $-$ 1) $\times$ 0.6
= 1 + 4 $\times$ 0.6 = 1 + 2.4 = 3.4
$\Delta {T_b} = {K_b} \times m \times i = 0.52 \times 1 \times 3.4 = 1.768^\circ $ C
$\Delta {T_b} = {({T_b})_{solution}} - {[{({T_b})_{{H_2}O}}]_{Solution}}$
$1.768 = {({T_b})_{solution}} - 100$
${({T_b})_{solution}} = 101.768^\circ $ C
$ = 375$ K
2021
Q137
JEE Mains
Numerical
14 Mar 2026
C6H6 freezes at 5.5$^\circ$C. The temperature at which a solution of 10g of C4H10 in 200g of C6H6 freeze is __________ $^\circ$C. (The molal freezing point depression constant of C6H6 is 5.12$^\circ$C/m.)
Correct Answer: 1
Explanation:
Pure solvent : C6H6(l)
Given,
$T_f^o = 5.5^\circ C$
${K_f} = 5.12^\circ C/m \Rightarrow m = 200g$
${m_{solute}} = 10g$
Molar mass of solute ${C_4}{H_{10}} = 12 \times 4 + 10 = 58$
Solute (C4H10) is non-dissociative;
$\therefore$ i = 1
$\therefore$ $\Delta {T_f} = i{K_f}\,m$
$ \Rightarrow (T_f^o - T_f^1) = 1 \times 5.12 \times {{(10/58)} \over {(200/1000)}}$
$5.5 - T_f^1 = {{5.12 \times 5 \times 10} \over {58}} \Rightarrow T_f^1 = 1.086^\circ C$
or $T_f^1 \approx 1^\circ C$
Given,
$T_f^o = 5.5^\circ C$
${K_f} = 5.12^\circ C/m \Rightarrow m = 200g$
${m_{solute}} = 10g$
Molar mass of solute ${C_4}{H_{10}} = 12 \times 4 + 10 = 58$
Solute (C4H10) is non-dissociative;
$\therefore$ i = 1
$\therefore$ $\Delta {T_f} = i{K_f}\,m$
$ \Rightarrow (T_f^o - T_f^1) = 1 \times 5.12 \times {{(10/58)} \over {(200/1000)}}$
$5.5 - T_f^1 = {{5.12 \times 5 \times 10} \over {58}} \Rightarrow T_f^1 = 1.086^\circ C$
or $T_f^1 \approx 1^\circ C$
2021
Q138
JEE Mains
Numerical
14 Mar 2026
When 9.45 g of CICH2COOH is added to 500 mL of water, its freezing point drops by 0.5°C. The dissociation constant of CICH2COOH is x $ \times $ 10-3.
The value of x is ________. (Rounded off to the nearest integer)
[Kf(H20) = 1.86 K kg mol-1]
The value of x is ________. (Rounded off to the nearest integer)
[Kf(H20) = 1.86 K kg mol-1]
Correct Answer: 34.4
Explanation:
Here, $i = {{Final\,moles} \over {Initial\,moles}}$
i = 1 $-$ $\alpha$ + $\alpha$ + $\alpha$ $\Rightarrow$ i = 1 + $\alpha$
Formula used for freezing point; $\Delta$Tf = i Kfm
Here, Kf = freezing constant of H2O
Kf(H2O) = 1.86 K kg mol$-$1
m = molarity
$\Delta$Tf = i Kfm
0.5 = (1 + $\alpha$) (1.86)${{(9.45/94.5)} \over {(500/1000)}}$
${5 \over {3.72}}$ = 1 + $\alpha$ $\Rightarrow$ ${5 \over {3.72}}$ $-$ 1 = $\alpha$
$\Rightarrow$ $\alpha$ $ = {{1.28} \over {3.72}} = {{32} \over {93}} = 0.344$
Percentage of dissociation = 34.4%
2021
Q139
JEE Advanced
Numerical
14 Mar 2026
The value of x is ________.
Correct Answer: 100.1
Explanation:
$
\begin{aligned}
& \mathrm{AgNO}_3(\mathrm{aq}) \longrightarrow \underset{0.1 ~ m}{\mathrm{Ag}^{+}(\mathrm{aq})}+\underset{0.1 ~m}{\mathrm{NO}_3^{-}(\mathrm{aq})}\\\\
& \Delta \mathrm{T}_{\mathrm{b}}=0.2 \times 0.5 \\\\
& =0.1^{\circ} \mathrm{C}=0.1 \mathrm{~K}
\end{aligned}
$
Boiling point of solution $=100.1^{\circ} \mathrm{C} =\mathrm{X} $
Boiling point of solution $=100.1^{\circ} \mathrm{C} =\mathrm{X} $
2021
Q140
JEE Advanced
Numerical
14 Mar 2026
The value of | y | is ________.
Correct Answer: 2.5
Explanation:
$
\begin{aligned}
& \mathrm{AgNO}_3(\mathrm{aq}) \longrightarrow \mathrm{Ag}^{+}(\mathrm{aq})+\mathrm{NO}_3^{-}(\mathrm{aq}) \\\\
& 0.05 \mathrm{~m} \quad\quad\quad\quad\quad 0.05 \mathrm{~m} \quad\quad 0.05 \mathrm{~m} \\\\
& \mathrm{BaCl}_2(\mathrm{aq}) \longrightarrow \mathrm{Ba}^{2+}(\mathrm{aq})+2 \mathrm{Cl}^{-}(\mathrm{aq}) \\\\
& 0.05 \mathrm{~m} \quad \quad\quad\quad\quad0.05 \mathrm{~m} \quad\quad 0.1 \mathrm{~m}
\end{aligned}
$
$\mathrm{Ag}^{+}$and $\mathrm{Cl}^{-}$combine to form $\mathrm{AgCl}$ precipitate
$ \begin{array}{cccc} & \mathrm{Ag}^{+}(\mathrm{aq})+ & \mathrm{Cl}^{-}(\mathrm{aq}) \longrightarrow & \mathrm{AgCl}(\mathrm{s}) \\\\ \mathrm{t}=0 & 0.05 \mathrm{~m} & 0.1 \mathrm{~m} \\\\ \mathrm{t}=\infty & 0 & 0.05 \mathrm{~m} \end{array} $
In final solution total concentration of all ions :
$ \begin{aligned} & {\left[\mathrm{Cl}^{-}\right]+\left[\mathrm{NO}_3^{-}\right]+\left[\mathrm{Ba}^{2+}\right]=0.05+0.05+0.05} \\\\ & \begin{aligned} \Delta \mathrm{T}_{\mathrm{b}} & =0.5 \times 0.15 \\\\ & =0.15 \mathrm{~m} \\\\ & =0.075^{\circ} \mathrm{C} \end{aligned} \end{aligned} $
B.P. of solution ' $\mathrm{B}$ ' $=100.075^{\circ} \mathrm{C}$
B.P. of solution ' $\mathrm{A}^{\prime}=100.1^{\circ} \mathrm{C}$
$|y|=100.1-100.075$
$ =0.025=2.5 \times 10^{-2} $
$\mathrm{Ag}^{+}$and $\mathrm{Cl}^{-}$combine to form $\mathrm{AgCl}$ precipitate
$ \begin{array}{cccc} & \mathrm{Ag}^{+}(\mathrm{aq})+ & \mathrm{Cl}^{-}(\mathrm{aq}) \longrightarrow & \mathrm{AgCl}(\mathrm{s}) \\\\ \mathrm{t}=0 & 0.05 \mathrm{~m} & 0.1 \mathrm{~m} \\\\ \mathrm{t}=\infty & 0 & 0.05 \mathrm{~m} \end{array} $
In final solution total concentration of all ions :
$ \begin{aligned} & {\left[\mathrm{Cl}^{-}\right]+\left[\mathrm{NO}_3^{-}\right]+\left[\mathrm{Ba}^{2+}\right]=0.05+0.05+0.05} \\\\ & \begin{aligned} \Delta \mathrm{T}_{\mathrm{b}} & =0.5 \times 0.15 \\\\ & =0.15 \mathrm{~m} \\\\ & =0.075^{\circ} \mathrm{C} \end{aligned} \end{aligned} $
B.P. of solution ' $\mathrm{B}$ ' $=100.075^{\circ} \mathrm{C}$
B.P. of solution ' $\mathrm{A}^{\prime}=100.1^{\circ} \mathrm{C}$
$|y|=100.1-100.075$
$ =0.025=2.5 \times 10^{-2} $
2020
Q141
JEE Mains
MCQ
14 Mar 2026
A set of solutions is prepared using 180 g of
water as a solvent and 10 g of different nonvolatile solutes A, B and C. The relative
lowering of vapour pressure in the presence of
these solutes are in the order :
[Given, molar mass of A = 100 g mol–1; B = 200 g mol–1; C = 10,000 g mol–1]
[Given, molar mass of A = 100 g mol–1; B = 200 g mol–1; C = 10,000 g mol–1]
A.
A > C > B
B.
C > B > A
C.
A > B > C
D.
B > C > A
2020
Q142
JEE Mains
MCQ
14 Mar 2026
The size of a raw mango shrinks to a much
smaller size when kept in a concentrated salt
solution. Which one of the following processes
can explain this?
A.
Osmosis
B.
Reverse osmosis
C.
Diffusion
D.
Dialysis
2020
Q143
JEE Mains
MCQ
14 Mar 2026
A graph of vapour pressure and temperature for three different liquids X, Y, and Z is shown below :
The following inferences are made :
(A) X has higher intermolecular interactions compared to Y.
(B) X has lower intermolecular interactions compared to Y.
(C) Z has lower intermolecular interactions compared to Y.
The correct inference (s) is / are :
The following inferences are made :
(A) X has higher intermolecular interactions compared to Y.
(B) X has lower intermolecular interactions compared to Y.
(C) Z has lower intermolecular interactions compared to Y.
The correct inference (s) is / are :
A.
(B)
B.
(A)
C.
(C)
D.
(A) and (C)
2020
Q144
JEE Mains
MCQ
14 Mar 2026
Two open beakers one containing a solvent and the other containing a mixture of that solvent
with a non voltatile solute are together selated in a container. Over time :
A.
The volume of the solution increases and the volume of the solvent decreases.
B.
The volume of solution does not change and the volume of the solvent decreases.
C.
The volumer of the solution and the solvent does not change.
D.
The volume of the solution decreases and the volume of the solvent increases.
2020
Q145
JEE Mains
MCQ
14 Mar 2026
At 35oC, the vapour pressure of CS2
is 512 mm. Hg and that of acetone is 344 mm Hg. A solution
of CS2
in acetone has a total vapour pressure of 600 mm Hg. The false statement amongst the
following is :
A.
CS2 and acetone are less attracted to each other than to themselves.
B.
a mixture of 100 ml. CS2 and 100 ml. acetone has a volume < 200 ml.
C.
Heat must be absorved in order to produce the solution 35oC
D.
Raoult's law is not obeyed by this system.
2020
Q146
JEE Mains
Numerical
14 Mar 2026
The elevation of boiling point of 0.10 m
aqueous CrCl3.xNH3 solution is two times that
of 0.05 m aqueous CaCl2 solution. The value of
x is ______.
[Assume 100% ionisation of the complex and CaCl2, coordination number of Cr as 6, and that all NH3 molecules are present inside the coordination sphere]
[Assume 100% ionisation of the complex and CaCl2, coordination number of Cr as 6, and that all NH3 molecules are present inside the coordination sphere]
Correct Answer: 5
Explanation:
Molality of CaCl2 solution = 0.05 m
$\Delta $Tb = i Kb m = 3 × Kb × 0.05 = 0.15 Kb
Molality of CrCl3.xNH3 = 0.10 m
$\Delta $Tb' = i Kb $ \times $ 0.10
Given, $\Delta $Tb' = 2$\Delta $Tb
$ \Rightarrow $ i Kb $ \times $ 0.10 = 0.15 Kb
$ \Rightarrow $ i = 3
Co-ordination number of Cr is 6.
[Cr(NH3 )x.Cl6-x]Cl3-6+x $ \to $ [Cr(NH3 )xCl] + (3-6+x)Cl–
i = 3 = 1 + 3 - 6 + x
$ \Rightarrow $ x = 5
$\Delta $Tb = i Kb m = 3 × Kb × 0.05 = 0.15 Kb
Molality of CrCl3.xNH3 = 0.10 m
$\Delta $Tb' = i Kb $ \times $ 0.10
Given, $\Delta $Tb' = 2$\Delta $Tb
$ \Rightarrow $ i Kb $ \times $ 0.10 = 0.15 Kb
$ \Rightarrow $ i = 3
Co-ordination number of Cr is 6.
[Cr(NH3 )x.Cl6-x]Cl3-6+x $ \to $ [Cr(NH3 )xCl] + (3-6+x)Cl–
i = 3 = 1 + 3 - 6 + x
$ \Rightarrow $ x = 5
2020
Q147
JEE Mains
Numerical
14 Mar 2026
The osmotic pressure of a solution of NaCl is
0.10 atm and that of a glucose solution is
0.20 atm. The osmotic pressure of a solution
formed by mixing 1 L of the sodium chloride
solution with 2 L of
the glucose solution is x $ \times $ 10–3 atm. x is _____. (nearest integer)
the glucose solution is x $ \times $ 10–3 atm. x is _____. (nearest integer)
Correct Answer: 167
Explanation:
For NaCl : $\pi $1 = 0.1 atm, v1 = 1 L
For Glucose: $\pi $2 = 0.2 atm, v2 = 2 L
$\pi $mix = ${{{\pi _1}{v_1} + {\pi _2}{v_2}} \over {{v_1} + {v_2}}}$
= ${{0.1 \times 1 + 0.2 \times 2} \over {1 + 2}}$
= ${{0.5} \over 3}$ = ${{500} \over 3} \times {10^{ - 3}}$
= 167 $ \times $ 10-3 atm
For Glucose: $\pi $2 = 0.2 atm, v2 = 2 L
$\pi $mix = ${{{\pi _1}{v_1} + {\pi _2}{v_2}} \over {{v_1} + {v_2}}}$
= ${{0.1 \times 1 + 0.2 \times 2} \over {1 + 2}}$
= ${{0.5} \over 3}$ = ${{500} \over 3} \times {10^{ - 3}}$
= 167 $ \times $ 10-3 atm
2020
Q148
JEE Mains
Numerical
14 Mar 2026
At 300 K, the vapour pressure of a solution
containing 1 mole of n-hexane and 3 moles of
n-heptane is 550 mm of Hg. At the same
temperature, if one more mole of n-heptane is
added to this solution, the vapour pressure of
the solution increases by 10 mm of Hg. What is
the vapour pressure in mm Hg of n-heptane in
its pure state ______?
Correct Answer: 600
Explanation:
Let X1 and P$P_1^o$
are the mole fraction and vapour
pressure of n-hexane in solution and X2 and $P_2^o$
are the mole fraction and vapour pressure of
n-heptane in solution then
550 = $P_1^o$$ \times $${1 \over 4}$ + $P_2^o$$ \times $${3 \over 4}$
$ \Rightarrow $ 2200 = $P_1^o$ + 3$P_2^o$ ....(1)
On addition of 1 more mole of n-heptane
560 = $P_1^o$$ \times $${1 \over 5}$ + $P_2^o$$ \times $${4 \over 5}$
$ \Rightarrow $ 2800 = $P_1^o$ + 4$P_2^o$ ....(2)
From (1) and (2),
$P_1^o$ = 400, $P_2^o$ = 600
550 = $P_1^o$$ \times $${1 \over 4}$ + $P_2^o$$ \times $${3 \over 4}$
$ \Rightarrow $ 2200 = $P_1^o$ + 3$P_2^o$ ....(1)
On addition of 1 more mole of n-heptane
560 = $P_1^o$$ \times $${1 \over 5}$ + $P_2^o$$ \times $${4 \over 5}$
$ \Rightarrow $ 2800 = $P_1^o$ + 4$P_2^o$ ....(2)
From (1) and (2),
$P_1^o$ = 400, $P_2^o$ = 600
2020
Q149
JEE Mains
Numerical
14 Mar 2026
If 250 cm3
of an aqueous solution containing 0.73 g of a protein A is isotonic with one litre of
another aqueous solution containing 1.65 g of a protein B, at 298 K, the ratio of the molecular
masses of A and B is ______ × 10–2 (to the nearest integer).
Correct Answer: 177
Explanation:
Let molar mass of protein A = x g/mol
Let molar mass of protein B = y g/mol
$\pi $A = osmotic pressure of protein A = ${{0.73} \over x} \times {{1000} \over {250}} \times RT$
$\pi $B = osmotic pressure of protein B = ${{1.65} \over y} \times {1 \over 1} \times RT$
Given $\pi $A = $\pi $B
$ \Rightarrow $ ${{0.73} \over x} \times {{1000} \over {250}} \times RT$ = ${{1.65} \over y} \times {1 \over 1} \times RT$
$ \Rightarrow $ ${x \over y}$ = ${{0.73} \over {0.25 \times 1.65}}$ = 1.77
= 177 $ \times $ 10-2
Let molar mass of protein B = y g/mol
$\pi $A = osmotic pressure of protein A = ${{0.73} \over x} \times {{1000} \over {250}} \times RT$
$\pi $B = osmotic pressure of protein B = ${{1.65} \over y} \times {1 \over 1} \times RT$
Given $\pi $A = $\pi $B
$ \Rightarrow $ ${{0.73} \over x} \times {{1000} \over {250}} \times RT$ = ${{1.65} \over y} \times {1 \over 1} \times RT$
$ \Rightarrow $ ${x \over y}$ = ${{0.73} \over {0.25 \times 1.65}}$ = 1.77
= 177 $ \times $ 10-2
2020
Q150
JEE Mains
Numerical
14 Mar 2026
A cylinder containing an ideal gas (0.1 mol of
1.0 dm3) is in thermal equilibrium with a large
volume of 0.5 molal aqueous solution of
ethylene glycol at its freezing point. If the
stoppers S1 and S2 (as shown in the figure) are
suddenly withdrawn, the volume of the gas in
litres after equilibrium is achieved will be____.
(Given, Kf (water) = 2.0 K kg mol–1,
R = 0.08 dm3 atm K–1 mol–1)
(Given, Kf (water) = 2.0 K kg mol–1,
R = 0.08 dm3 atm K–1 mol–1)
Correct Answer: 2.17TO2.23
Explanation:
For aqueous solution
$\Delta $Tf = Kf.m = 2 × 0.5
$ \therefore $ Temperature of solution = –1°C = 272 K
$ \therefore $ Final volume of ideal gas = ${{nRT} \over P}$
= ${{0.1 \times 0.08 \times 272} \over 1}$
= 2.18 L
$\Delta $Tf = Kf.m = 2 × 0.5
$ \therefore $ Temperature of solution = –1°C = 272 K
$ \therefore $ Final volume of ideal gas = ${{nRT} \over P}$
= ${{0.1 \times 0.08 \times 272} \over 1}$
= 2.18 L