For a dilute solution containing 2.5g of a non-volatile non-electrolyte solute in 100g of water, the elevation in boiling point at 1 atm pressure is `2^(@)"C"`. Assuming concentration of solute is much lower than the concentration of solvent, the vapour pressure (mm of Hg) of the solution is (take `K_(b)`=0.76 K kg `"mol"^(-1)`)

Options

A. 724
B. 740
C. 736
D. 718

Answer

A

Explanation

`Delta T_(b)=K_(b)xx m`
`2=(0.76xx2.5//M)/(0.1)rArr M=9.5`
Since solute is present in less amount
`(P^(@)-P_(s))/(P^(@))=(n)/(N)`
`(760-P_(s))/(760)=(2.5//9.5)/(100//18)rArr P_(s)=724`