Question

The mole fraction of solute in 10% (w/w) aqueous NaOH solution is:

• A. $0.1$
• B. $0.05$
• C. $0.0476$
• D. $0.075$

Answer 1

Answer: (C)

$0.0476$

$10$% $\omega /\omega$ $=10$ gm solute in 100 gm solution.

So, the weight of solvent is 90 gm.

Moles of NaOH $=$ $\frac{10}{40}$

Moles of solvent (water) $=\frac{90}{18}=5$

Hence, mole fraction of solute $=\frac{0.25}{0.25+5}=\frac{1}{21}$.

$=0.0476$