The vapour pressure of water at $20\,^{\circ}C$ is $17.54\,mm$. When $20\,g$ of a non-ionic substance is dissolved in $100\,g$ of water,the vapour pressure is lowered by $0.30\,mm$. What is the molecular weight of the substance?

The vapour pressure of a solvent $A$ is $0.80 \, atm$. When a non-volatile substance $B$ is added to this solvent its vapour pressure drops to $0.6 \, atm$. What is the mole fraction of $B$ in the solution?

How many grams of a non-volatile solute (molar mass $40 \ g/mol$) must be added to $114 \ g$ of octane to reduce its vapour pressure by $20\%$ (in $g$)?

Which of the following will have the lowest vapor pressure?

Lowering of vapour pressure due to a solute in $1 \, molal$ aqueous solution at $100 \, ^\circ C$ is ........ $torr$.

In a mixture of liquids $A$ and $B$,if the mole fractions of component $A$ in vapour phase and liquid mixture are $x_1$ and $x_2$ respectively,then the total vapour pressure of liquid mixture is (where $P_{A}^{\circ}$ and $P_{B}^{\circ}$ are the vapour pressures of pure $A$ and $B$)