Determination of Lowering of Vapour Pressure

The temperature at which the vapour pressure of a liquid equals the external pressure is called

Vapour pressure of a solvent is $17.5 \mathrm{mm}$ $\mathrm{Hg}$ while that of its dilute solution is $17.45$. What will be the mole fraction of the solvent?

The vapour pressure of pure water at $25°\mathrm{C}$ is $23.62 \mathrm{mm}$ $\mathrm{Hg}$, What will be the vapour pressure of a solution of $1.5 \mathrm{g}$ of urea in $50 \mathrm{g}$ of water?

Give your answer up to two decimal places.

In an Ostwald-Walker experiment, dry air was first blown through a solution containing a certain amount of solute $(\mathrm{M}=278)$ in $150 \mathrm{g}$ of water and then also through pure water. The loss in mass of water was found to be $0.0827 \mathrm{g}$, while the mass of water absorbed in sulphuric acid was $3.317 \mathrm{g}$. Calculate the amount of the solute.

Give your answer up to two decimal places without rounding-off.

The vapour pressure of a $0.01 \mathrm{m}$ solution of a weak base $\mathrm{BOH}$ in water at $20°\mathrm{C}$ is $17.536 \mathrm{mm}.$ Calculate ${\mathrm{K}}_{\mathrm{b}}$ for the base. Aqueous tension at $20°\mathrm{C}=17.54 \mathrm{mm}$. (Give answer as ${\mathrm{K}}_{\mathrm{b}} \times {10}^4$ )

[Hint $\mathrm{i}=\frac{\text{ observed lowering in}\mathrm{vapour} \mathrm{pressure}}{\text{ calculated lowering in vapour pressure }}=\frac{\mathrm{p}-{\mathrm{p}}_{\text{obs. }}}{{\mathrm{p}}^0·\frac{\mathrm{n}}{\mathrm{N}}}=\frac{17.540-17.536}{17.54\times \frac{0.01}{1000/18}},$

Then apply $\mathrm{i}=1+\mathrm{x}$ and ${\mathrm{K}}_{\mathrm{b}}=\frac{0.01{\mathrm{x}}^2}{1-\mathrm{x}}$]

Which of the following aqueous solutions has a higher vapour pressure if the density of water is $1 \mathrm{g}/\mathrm{cc}?$

(a) Solution having mole fraction of cane sugar=$0.1$

(b) Solution having molal concentration=$1 \mathrm{m}$

$0.5 \mathrm{g}$ of a non-volatile organic compound (Molar weight=$65$) is dissolved in $100 \mathrm{mL}$ of ${\mathrm{CCl}}_4.$ If the vapour pressure of pure ${\mathrm{CCl}}_4$ is $143 \mathrm{mm} \mathrm{Hg}$, what would be the vapour pressure of the solution? (Density of ${\mathrm{CCl}}_4$ solution is $1.58 \mathrm{g}/\mathrm{cc}$.)

At $20°\mathrm{C}$, the vapour pressure of ether is $442 \mathrm{mm}$. When $6.1 \mathrm{g}$ of a substance is dissolved in $50 \mathrm{g}$ of ether (molar weight=$74$), the vapour pressure falls to $410 \mathrm{mm}$. What is the molecular weight of the substance?

The vapour pressure of an aqueous solution of cane sugar (molar weight=$342$) is $756 \mathrm{mm}$ at $100°\mathrm{C}$. How many grams of sugar are present per $1000 \mathrm{g}$ of water?

What is the vapour pressure of a solution containing $15.6 \mathrm{g}$ of water and $1.68 \mathrm{g}$ of sucrose $\left({\mathrm{C}}_{12}{\mathrm{H}}_{22}{\mathrm{O}}_{11}\right)$ at $100° \mathrm{C}$?

Give your answer up to two decimal places. Molecular weight of sucrose is $342$.

The pressure of the water vapour of a solution containing a non-volatile solute is $2\%$ below that of the vapour of pure water. Determine the molality of the solution.

Give your answer up to three decimal places.