Vapour pressure of a solution of 5 g of non-electrolyte in 100 g of water at a particular temperature is `2985 N//m^2`. The vapour pressure of pure water is `3000 N/m^2`, the molecular weight of the solute is

Options

A. 90
B. 200
C. 180
D. 380

Answer

C

Explanation

`M_2 = (w_2 M_1xx P^@)/(w_1 (P^@-P_s))`
Where, `M_2` = molar mass of solute, `w_2` = weight of solute
`M_1` = molar mass of solvent, `w_1` = weight of solvent
`p^@` = vapour pressure of pure solvent
`P_s` = vapour pressure of solution
`=(5xx18 xx 3000)/(100xx(3000 - 2985))=180`