Colligative property measurement is one of the techniques used in the measurement of chemical quantities with reasonable accuracy.
If a 40.65 gm sample of `K_2SO_4` and `BaSO_4` is dissolved in 900 gm of pure water to form a solution 'A' at `57^@C`.Its vapours pressure is found to be 39.6 torr while vapour pressure of pure water at `57^@C` is 40 torr. Density of solution A is 1.24g/ml.
In a different experiment when small amount of pure `BaSO_4` is mixed with water at `57^@C` it gives the osomotic rise at `4.05xx10^(-5)` atm.
`(R=0.082 Lt.-atm//"mol"-K,K=39,Ba=137,S=32,O=16)`
Elevation in boiling point of solution A is `(K_b "water"=0.54 K-kg//mol)`:

Options

A. `65.75%`
B. `72%`
C. `60.35%`
D. `78.74%`

Answer

B

Explanation

`(40-39.6)/39.6=(3xxx/174)/50`
x=29.29 g
`%=29.29/40.65xx100=72%`