The mass of a non-volatile solute (molar mass 80 g `mol^(-1)` ) which should be dissolved in 92g of toluene to reduce its vapour pressure to `90%`

Options

A. 10g
B. 20g
C. `9.2g`
D. `8.89g`

Answer

D

Explanation

`(Delta P )/(P ^(@))=x _(2)`
`(100-90)/(100) = (n _(2))/(n _(2) + n _(1)) implies (n _(2) + n _(1))/(n _(2)) = (100)/*(10) [ n _(1) = (92)/(92) =1]`
`1+ (1)/(n _(2)) =10`
`(1)/( n _(2)) = 9 implies n _(2) = (1)/(9)`
`implies (W_(2))/(M _(2))= 1/9 implies W_(2) = (M_(2))/(9)`
` W _(2)= (80)/(9) =89g.`