02. Lowering of Vapour Pressure
SOLUTIONS

277301 The vapour pressure of a solvent decreased by $10 \mathrm{~mm}$ of mercury when a non-volatile solute was added to the solvent. The mol fraction of the solute in the solution is 0.2 . What should be the mole fraction of the solvent if the decrease in the vapour pressure is to be $20 \mathrm{~mm}$ of mercury ?

1 0.4
2 0.6
3 0.8
4 0.2
SOLUTIONS

277305 The freezing point of an aqueous solution containing $25 \mathrm{~g}$ of ethanol in $1000 \mathrm{~g}$ of $\mathrm{H}_{2} \mathrm{O}$ is $\left[K_{\mathrm{f}}=1.86 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}\right]$

1 $0.25^{\circ} \mathrm{C}$
2 $0.5^{\circ} \mathrm{C}$
3 $-1.5^{\circ} \mathrm{C}$
4 $-1^{\circ} \mathrm{C}$
SOLUTIONS

277306 The vapour pressure of pure liquids $A$ and $B$ are 450 and $700 \mathrm{~mm}$ at $\mathrm{Hg}$ of $350 \mathrm{~K}$ respectively. If the total vapour pressure of the mixture is $600 \mathrm{~mm}$ of $\mathrm{Hg}$, the composition of the mixture in the solution is

1 $\mathrm{x}_{\mathrm{A}}=0.4$ and $\mathrm{x}_{\mathrm{B}}=0.6$
2 $\mathrm{x}_{\mathrm{A}}=0.6$ and $\mathrm{x}_{\mathrm{B}}=0.4$
3 $\mathrm{x}_{\mathrm{A}}=0.3$ and $\mathrm{x}_{\mathrm{B}}=0.7$
4 $\mathrm{x}_{\mathrm{A}}=0.7$ and $\mathrm{x}_{\mathrm{B}}=0.3$
SOLUTIONS

277307 Henry's law constant for the solubility of $\mathrm{N}_{2}$ gas in water at $298 \mathrm{~K}$ is $1.0 \times 10^{5} \mathrm{~atm}$. The mole fraction of $\mathrm{N}_{2}$ in air is 0.8 . The number of moles of $\mathrm{N}_{2}$ from air dissolved in 10 moles of water at $298 \mathrm{~K}$ and $5 \mathbf{a t m}$ pressure is

1 $4.0 \times 10^{-4}$
2 $4.0 \times 10^{-5}$
3 $5.0 \times 10^{-4}$
4 $4.0 \times 10^{-6}$
SOLUTIONS

277308 The correct option for the value of vapour pressure of a solution at $45^{\circ} \mathrm{C}$ with benzene to octane in molar ratio $3: 2$ is
[At $45^{\circ} \mathrm{C}$ pressure of benzene is $280 \mathrm{~mm} \mathrm{Hg}$ and that of octance is $420 \mathrm{~mm} \mathrm{Hg}$. Assume ideal gas]

1 $350 \mathrm{~mm}$ of $\mathrm{Hg}$
2 $160 \mathrm{~mm}$ of $\mathrm{Hg}$
3 $168 \mathrm{~mm}$ of $\mathrm{Hg}$
4 $336 \mathrm{~mm}$ of $\mathrm{Hg}$
SOLUTIONS

277301 The vapour pressure of a solvent decreased by $10 \mathrm{~mm}$ of mercury when a non-volatile solute was added to the solvent. The mol fraction of the solute in the solution is 0.2 . What should be the mole fraction of the solvent if the decrease in the vapour pressure is to be $20 \mathrm{~mm}$ of mercury ?

1 0.4
2 0.6
3 0.8
4 0.2
SOLUTIONS

277305 The freezing point of an aqueous solution containing $25 \mathrm{~g}$ of ethanol in $1000 \mathrm{~g}$ of $\mathrm{H}_{2} \mathrm{O}$ is $\left[K_{\mathrm{f}}=1.86 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}\right]$

1 $0.25^{\circ} \mathrm{C}$
2 $0.5^{\circ} \mathrm{C}$
3 $-1.5^{\circ} \mathrm{C}$
4 $-1^{\circ} \mathrm{C}$
SOLUTIONS

277306 The vapour pressure of pure liquids $A$ and $B$ are 450 and $700 \mathrm{~mm}$ at $\mathrm{Hg}$ of $350 \mathrm{~K}$ respectively. If the total vapour pressure of the mixture is $600 \mathrm{~mm}$ of $\mathrm{Hg}$, the composition of the mixture in the solution is

1 $\mathrm{x}_{\mathrm{A}}=0.4$ and $\mathrm{x}_{\mathrm{B}}=0.6$
2 $\mathrm{x}_{\mathrm{A}}=0.6$ and $\mathrm{x}_{\mathrm{B}}=0.4$
3 $\mathrm{x}_{\mathrm{A}}=0.3$ and $\mathrm{x}_{\mathrm{B}}=0.7$
4 $\mathrm{x}_{\mathrm{A}}=0.7$ and $\mathrm{x}_{\mathrm{B}}=0.3$
SOLUTIONS

277307 Henry's law constant for the solubility of $\mathrm{N}_{2}$ gas in water at $298 \mathrm{~K}$ is $1.0 \times 10^{5} \mathrm{~atm}$. The mole fraction of $\mathrm{N}_{2}$ in air is 0.8 . The number of moles of $\mathrm{N}_{2}$ from air dissolved in 10 moles of water at $298 \mathrm{~K}$ and $5 \mathbf{a t m}$ pressure is

1 $4.0 \times 10^{-4}$
2 $4.0 \times 10^{-5}$
3 $5.0 \times 10^{-4}$
4 $4.0 \times 10^{-6}$
SOLUTIONS

277308 The correct option for the value of vapour pressure of a solution at $45^{\circ} \mathrm{C}$ with benzene to octane in molar ratio $3: 2$ is
[At $45^{\circ} \mathrm{C}$ pressure of benzene is $280 \mathrm{~mm} \mathrm{Hg}$ and that of octance is $420 \mathrm{~mm} \mathrm{Hg}$. Assume ideal gas]

1 $350 \mathrm{~mm}$ of $\mathrm{Hg}$
2 $160 \mathrm{~mm}$ of $\mathrm{Hg}$
3 $168 \mathrm{~mm}$ of $\mathrm{Hg}$
4 $336 \mathrm{~mm}$ of $\mathrm{Hg}$
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SOLUTIONS

277301 The vapour pressure of a solvent decreased by $10 \mathrm{~mm}$ of mercury when a non-volatile solute was added to the solvent. The mol fraction of the solute in the solution is 0.2 . What should be the mole fraction of the solvent if the decrease in the vapour pressure is to be $20 \mathrm{~mm}$ of mercury ?

1 0.4
2 0.6
3 0.8
4 0.2
SOLUTIONS

277305 The freezing point of an aqueous solution containing $25 \mathrm{~g}$ of ethanol in $1000 \mathrm{~g}$ of $\mathrm{H}_{2} \mathrm{O}$ is $\left[K_{\mathrm{f}}=1.86 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}\right]$

1 $0.25^{\circ} \mathrm{C}$
2 $0.5^{\circ} \mathrm{C}$
3 $-1.5^{\circ} \mathrm{C}$
4 $-1^{\circ} \mathrm{C}$
SOLUTIONS

277306 The vapour pressure of pure liquids $A$ and $B$ are 450 and $700 \mathrm{~mm}$ at $\mathrm{Hg}$ of $350 \mathrm{~K}$ respectively. If the total vapour pressure of the mixture is $600 \mathrm{~mm}$ of $\mathrm{Hg}$, the composition of the mixture in the solution is

1 $\mathrm{x}_{\mathrm{A}}=0.4$ and $\mathrm{x}_{\mathrm{B}}=0.6$
2 $\mathrm{x}_{\mathrm{A}}=0.6$ and $\mathrm{x}_{\mathrm{B}}=0.4$
3 $\mathrm{x}_{\mathrm{A}}=0.3$ and $\mathrm{x}_{\mathrm{B}}=0.7$
4 $\mathrm{x}_{\mathrm{A}}=0.7$ and $\mathrm{x}_{\mathrm{B}}=0.3$
SOLUTIONS

277307 Henry's law constant for the solubility of $\mathrm{N}_{2}$ gas in water at $298 \mathrm{~K}$ is $1.0 \times 10^{5} \mathrm{~atm}$. The mole fraction of $\mathrm{N}_{2}$ in air is 0.8 . The number of moles of $\mathrm{N}_{2}$ from air dissolved in 10 moles of water at $298 \mathrm{~K}$ and $5 \mathbf{a t m}$ pressure is

1 $4.0 \times 10^{-4}$
2 $4.0 \times 10^{-5}$
3 $5.0 \times 10^{-4}$
4 $4.0 \times 10^{-6}$
SOLUTIONS

277308 The correct option for the value of vapour pressure of a solution at $45^{\circ} \mathrm{C}$ with benzene to octane in molar ratio $3: 2$ is
[At $45^{\circ} \mathrm{C}$ pressure of benzene is $280 \mathrm{~mm} \mathrm{Hg}$ and that of octance is $420 \mathrm{~mm} \mathrm{Hg}$. Assume ideal gas]

1 $350 \mathrm{~mm}$ of $\mathrm{Hg}$
2 $160 \mathrm{~mm}$ of $\mathrm{Hg}$
3 $168 \mathrm{~mm}$ of $\mathrm{Hg}$
4 $336 \mathrm{~mm}$ of $\mathrm{Hg}$
SOLUTIONS

277301 The vapour pressure of a solvent decreased by $10 \mathrm{~mm}$ of mercury when a non-volatile solute was added to the solvent. The mol fraction of the solute in the solution is 0.2 . What should be the mole fraction of the solvent if the decrease in the vapour pressure is to be $20 \mathrm{~mm}$ of mercury ?

1 0.4
2 0.6
3 0.8
4 0.2
SOLUTIONS

277305 The freezing point of an aqueous solution containing $25 \mathrm{~g}$ of ethanol in $1000 \mathrm{~g}$ of $\mathrm{H}_{2} \mathrm{O}$ is $\left[K_{\mathrm{f}}=1.86 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}\right]$

1 $0.25^{\circ} \mathrm{C}$
2 $0.5^{\circ} \mathrm{C}$
3 $-1.5^{\circ} \mathrm{C}$
4 $-1^{\circ} \mathrm{C}$
SOLUTIONS

277306 The vapour pressure of pure liquids $A$ and $B$ are 450 and $700 \mathrm{~mm}$ at $\mathrm{Hg}$ of $350 \mathrm{~K}$ respectively. If the total vapour pressure of the mixture is $600 \mathrm{~mm}$ of $\mathrm{Hg}$, the composition of the mixture in the solution is

1 $\mathrm{x}_{\mathrm{A}}=0.4$ and $\mathrm{x}_{\mathrm{B}}=0.6$
2 $\mathrm{x}_{\mathrm{A}}=0.6$ and $\mathrm{x}_{\mathrm{B}}=0.4$
3 $\mathrm{x}_{\mathrm{A}}=0.3$ and $\mathrm{x}_{\mathrm{B}}=0.7$
4 $\mathrm{x}_{\mathrm{A}}=0.7$ and $\mathrm{x}_{\mathrm{B}}=0.3$
SOLUTIONS

277307 Henry's law constant for the solubility of $\mathrm{N}_{2}$ gas in water at $298 \mathrm{~K}$ is $1.0 \times 10^{5} \mathrm{~atm}$. The mole fraction of $\mathrm{N}_{2}$ in air is 0.8 . The number of moles of $\mathrm{N}_{2}$ from air dissolved in 10 moles of water at $298 \mathrm{~K}$ and $5 \mathbf{a t m}$ pressure is

1 $4.0 \times 10^{-4}$
2 $4.0 \times 10^{-5}$
3 $5.0 \times 10^{-4}$
4 $4.0 \times 10^{-6}$
SOLUTIONS

277308 The correct option for the value of vapour pressure of a solution at $45^{\circ} \mathrm{C}$ with benzene to octane in molar ratio $3: 2$ is
[At $45^{\circ} \mathrm{C}$ pressure of benzene is $280 \mathrm{~mm} \mathrm{Hg}$ and that of octance is $420 \mathrm{~mm} \mathrm{Hg}$. Assume ideal gas]

1 $350 \mathrm{~mm}$ of $\mathrm{Hg}$
2 $160 \mathrm{~mm}$ of $\mathrm{Hg}$
3 $168 \mathrm{~mm}$ of $\mathrm{Hg}$
4 $336 \mathrm{~mm}$ of $\mathrm{Hg}$
SOLUTIONS

277301 The vapour pressure of a solvent decreased by $10 \mathrm{~mm}$ of mercury when a non-volatile solute was added to the solvent. The mol fraction of the solute in the solution is 0.2 . What should be the mole fraction of the solvent if the decrease in the vapour pressure is to be $20 \mathrm{~mm}$ of mercury ?

1 0.4
2 0.6
3 0.8
4 0.2
SOLUTIONS

277305 The freezing point of an aqueous solution containing $25 \mathrm{~g}$ of ethanol in $1000 \mathrm{~g}$ of $\mathrm{H}_{2} \mathrm{O}$ is $\left[K_{\mathrm{f}}=1.86 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}\right]$

1 $0.25^{\circ} \mathrm{C}$
2 $0.5^{\circ} \mathrm{C}$
3 $-1.5^{\circ} \mathrm{C}$
4 $-1^{\circ} \mathrm{C}$
SOLUTIONS

277306 The vapour pressure of pure liquids $A$ and $B$ are 450 and $700 \mathrm{~mm}$ at $\mathrm{Hg}$ of $350 \mathrm{~K}$ respectively. If the total vapour pressure of the mixture is $600 \mathrm{~mm}$ of $\mathrm{Hg}$, the composition of the mixture in the solution is

1 $\mathrm{x}_{\mathrm{A}}=0.4$ and $\mathrm{x}_{\mathrm{B}}=0.6$
2 $\mathrm{x}_{\mathrm{A}}=0.6$ and $\mathrm{x}_{\mathrm{B}}=0.4$
3 $\mathrm{x}_{\mathrm{A}}=0.3$ and $\mathrm{x}_{\mathrm{B}}=0.7$
4 $\mathrm{x}_{\mathrm{A}}=0.7$ and $\mathrm{x}_{\mathrm{B}}=0.3$
SOLUTIONS

277307 Henry's law constant for the solubility of $\mathrm{N}_{2}$ gas in water at $298 \mathrm{~K}$ is $1.0 \times 10^{5} \mathrm{~atm}$. The mole fraction of $\mathrm{N}_{2}$ in air is 0.8 . The number of moles of $\mathrm{N}_{2}$ from air dissolved in 10 moles of water at $298 \mathrm{~K}$ and $5 \mathbf{a t m}$ pressure is

1 $4.0 \times 10^{-4}$
2 $4.0 \times 10^{-5}$
3 $5.0 \times 10^{-4}$
4 $4.0 \times 10^{-6}$
SOLUTIONS

277308 The correct option for the value of vapour pressure of a solution at $45^{\circ} \mathrm{C}$ with benzene to octane in molar ratio $3: 2$ is
[At $45^{\circ} \mathrm{C}$ pressure of benzene is $280 \mathrm{~mm} \mathrm{Hg}$ and that of octance is $420 \mathrm{~mm} \mathrm{Hg}$. Assume ideal gas]

1 $350 \mathrm{~mm}$ of $\mathrm{Hg}$
2 $160 \mathrm{~mm}$ of $\mathrm{Hg}$
3 $168 \mathrm{~mm}$ of $\mathrm{Hg}$
4 $336 \mathrm{~mm}$ of $\mathrm{Hg}$