Question

An ‘x’ molal solution of a compound in benzene has mole fraction of solute equal to 0.2. The value of ‘x’ is

• A. 3.2
• B. 5.2
• C. 7.2
• D. 8.2

Answer 1

The correct option is A 3.2

X molal defines that X moles are present in 1Kg of benzene

Hence mole fraction of solute is given by

$MoleFraction=\frac{Numberofmolesofsolute}{Numberofmolesofsolute+Numberofmolesofsolvent}$

$Molefraction=\frac{X}{X+\frac{1000}{78}}$

$Molefraction=\frac{X}{X+12.82}=0.2$

$X=0.2X+12.82\times 0.2$

$X=3.2$