An aqueous solution of volume V ml contains a non-volatile solute of unknown mass $W_B \mathrm{~g}$ and molar mass $M_B \mathrm{~g} / \mathrm{mol}$. If the Osmotic pressure of the solution is 1.013 bar, which one of the following is the mathematical expression to be used to calculate $W_B$ ?

The ratio of $\mathrm{N}_2$ and $\mathrm{O}_2$ gases in the atmosphere is $4: 1$. The ratio of the mole fractions of the dissolved gases $\mathrm{N}_2$ : $\mathrm{O}_2$ in rain water will be approximately ........ (At $293 \mathrm{~K}, \mathrm{~K}_{\mathrm{H}}$ for Nitrogen and Oxygen in kbar units are 76.48 and 34.86 respectively.)

At 300 K the vapour pressure of an ideal solution containing 1.0 mole each of volatile liquids X and Y is 1000 mm . Keeping the temperature constant, when 2.0 moles of liquid X is added to the solution, its vapour pressure increases by 200 mm . Calculate the vapour pressure of X and Y in their pure state

Lead storage battery contains $4.25 \mathrm{M} \mathrm{H}_2 \mathrm{SO}_4$ which has a density of $1.24 \mathrm{~g} / \mathrm{ml}$. Calculate the molality of aqueous solution of $\mathrm{H}_2 \mathrm{SO}_4$.