Mole fraction of a solute in an aqueous solution is 0.2. The molality of the solution will be

Options

A. `3.2`
B. 2
C. 4
D. 3.4

Answer

A

Explanation

`x_(S)=(n_(S))/(n_(S)+n_(B))=0.2`
Let `n_(S)=0.2 rArr n_(B) = 0.8`
Molar mass of benzene `(C_(6)H_(6)) = 78g mol^(-1)`
Mass of benzene `= 0.8xx78=62.4 g=0.0624 kg`
Molarity `= (0.2)/(0.0624) mol kg^(-1) = 3.2 m`