Question

What will be the mole fraction of water present in $10$ molal aqueous solution of $NaOH$?

• A. $0.95$
• B. $0.32$
• C. $0.68$
• D. $0.84$

Answer 1

The correct option is D $0.84$

$4$ molal aqueos solution means $10$ moles of $NaOH$ (solute) is present in $1000\text{g}$ of water (solvent)
Number of moles of water $=\frac{1000}{18}=55.56$
$\text{Mole fraction (solvent)}=\frac{\text{moles of solvent}}{\text{moles of solute + moles of solvent}}$
$\text{Mole fraction of water}=\frac{55.56}{55.56+10}=\frac{55.56}{65.56}=0.84$