Solution P contains $3.6 g$ glucose (molar mass $180$ ) in $100 g$ of water. Solution Q contains $w g$ of $NaCl$ (molar mass $58.5$ ) in $100 g$ of water and has the same vapour pressure as P. Assume complete dissociation of $NaCl$ and take $M (H X_{2} O) = 18$ . Which statements are correct?

Answer: A, B, D

Equal vapour pressure with equal water mass needs equal particle moles. P has

3.6/180 = 0.0200 mol

. NaCl gives 2 particles per unit, so

n_{NaCl} = 0.0100 mol

and

w = 0.0100 \times 58.5 = 0.585 g

(statements 1 and 2 true, 3 false). Relative lowering of P

= 0.0200/ (5.556 + 0.0200) = 3.587 \times 1 0^{- 3}

(true). Answer: 1, 2 and 4.