Question

What is the mole fraction of the solute in $2.5$ molal aqueous solution?

• A. $0.043$
• B. $0.053$
• C. $0.063$
• D. $0.073$

Answer 1

Answer: (A)

$0.043$

Answer 2

$2.5$ molal solution means $2.5$ moles of solute are present in $1000 \,mL$ solution (in aqueous solution) moles of water
$= \frac{1000}{18}$
$= 55.55\,mol$
$\therefore$ Mole fraction of solute
$= \frac{n_1}{n_1 +n_2}$
$= \frac{2.5}{2.5 + 55.5}$
$= \frac{2.5}{58.05}$
$= 0.043$