8 g of NaOH is dissolved in 18 g of $\mathrm{H}_{2} \mathrm{O}$. Mole fraction of NaOH in solution and molality (in $\mathrm{mol} \mathrm{kg}^{-1}$) of the solution respectively are :

JEE Main · 2019 · 12 Jan 2019 · Shift 2 · Some Basic Concepts of Chemistry

8 g of NaOH is dissolved in 18 g of

H_{2} O

. Mole fraction of NaOH in solution and molality (in

mol kg^{- 1}

) of the solution respectively are :

Answer: (C)

With

8

g of

NaOH

, that is

\frac{8}{40} = 0.2

mol, in

18

g of water,

\frac{18}{18} = 1

mol, the mole fraction of

NaOH

\frac{0.2}{0.2 + 1} = 0.167

. The molality, moles of solute per kilogram of solvent, is

\frac{0.2}{0.018} = 11.11 mol k g^{- 1}

JEE Main · 2019 · 12 Jan 2019 · Shift 2 · Single correct option