What will be the mass of a non-volatile solute ( Molar mass ` = 40 g mol ^(-1))`
Which should be dissolved in 114 g octane to reduce its vapour pressure to `80 %`

Options

A. 10 g
B. 4 g
C. 2 g
D. 16 g

Answer

A

Explanation

`( P ^(@) P _(S))/( P _(S))= ( n )/( n )`
`( P ^(@) - 0. 8 P ^(@))/( 0. 8 P ) = ( (x)/( 40))/( ( 114)/( 114)) = ( 0. 2 p ^(@))/( 0. 8 p ^(@)) = (x)/(40)`
`x = 10 ` gram
Therefore , the mass of non-volatile solute is 10 gm.