AIEEE 2011 Solved Paper

The formula between Mole fraction and Molality is
m=‌

X‌solute ‌

X‌solvent ‌

×‌

1000

M‌solvent ‌

m= molality, X‌solute ‌= Mole fraction of solute, X‌solvent ‌= Mole fraction of solvent, M‌solvent ‌= Molar mass of solvent
Here solute is methyl alcohol (CH3‌OH) and solvent is water (H2O). Here water is solvent because question says solution is aqueous.
Assume mole fraction of methyl alcohol =X
So mole fraction of water =1−X
and given molality (m)=5.2
M‌solvent ‌=18 (as molar mass of H2O=18 )
∴5.2=‌

X

1−X

×‌

1000

18

by solving this we get,
X=0.086