A solution containing 0.1g of a non-volatile organic substance P (molecular mass 100) in 100g of benzene raises the boiling point of benzene by `0.2^(@)C`, while a solution containing 0.1 g of another non-volatile substance Q in the same amount of benzene raises the boiling point of benzene by `0.4^(@)C`. What is the ratio of molecular masses of P and Q ?

Options

A. `1 : 2`
B. `2 : 1`
C. `1 : 4`
D. `4 : 1`

Answer

B

Explanation

`((DeltaT)_(P))/((DeltaT)_(Q))=(K_(b)xx((w_(B)xx1000)/(m_(B)xxw_(A)))_(P))/(K_(b)xx((w_(B)xx1000)/(m_(B)xxw_(A)))_(Q))`
`(0.2)/(0.4)=(((0.1xx1000)/(100xx100))_(P))/(((0.1xx1000)/(100xxm_(B)))_(Q))`
`(1)/(2)=((m_(B))_(Q))/(100)`
`m_(B)=50`
`:.(m_(B))_(P):(m_(B))_(Q)=100:50`
`=2:1`]