Question

A solution is prepared by dissolving 15.0 g of NH3 in 250 g of water. The density of the resulting solution is 0.974 g/mL. The mole fraction of NH3 in the solution is _____.A) 16.8B) 0.940C) 0.0597D) 0.922E) 0.0640

Answer 1

Answer:

Mole fraction of $NH_{3}$ in solution is 0.0597.

Explanation:

Molar mass of $NH_{3}$ = 17.031 g/mol

Molar mass of $H_{2}O$ = 18.015 g/mol

No. of moles = (mass)/(molar mass)

So, 15.0 g of $NH_{3}$ = $\frac{15.0}{17.031}$ moles of $NH_{3}$ = 0.8807 moles of $NH_{3}$

      250 g of $H_{2}O$ = $\frac{250}{18.015}$ moles of $H_{2}O$ = 13.88 moles of $H_{2}O$

So, Mole fraction of $NH_{3}$ in the solution = (no.of moles of $NH_{3}$ )/(total no. of moles) = $\frac{0.8807}{0.8807+13.88}$ = 0.0597

Hence, mole fraction of $NH_{3}$ in solution is 0.0597.