The mole fraction of ethanol in an aqueous solution is 0.1. Then find its molality ? 

Mole fraction ethanol (solute),  ${\text{X}}_{\text{A}}=0.1$

Mole fraction of water (solvent) $X_B=1-0.1=0.9$

Gram molecular weight of water,  ${\left(GMW\right)}_B=18g/mol$

Then, molality of solution is,

$\text{m}=\frac{0.1\times 1000}{0.9\times 18}=6.17$