Question

The molarity of an aqueous solution of glycol is $12\text{M}$. The density of the solution is $1.392\text{g/mL}$. Find the mole fraction of glycol.
(Given, molar mass of glycol $=62\text{g/mol}$)

• A. $0.5$
• B. $0.25$
• C. $0.75$
• D. $0.9$

Answer 1

The correct option is B $0.25$

Given:
Molarity of the solution $=12\text{M}$
Assuming $\text{1 L}$ of the solution,
Moles of ethylene glycol $=12\text{mol}$
Molar mass of ethylene glycol $=62\text{g/mol}$ (given)
Mass of ethylene glycol $=62\times 12=744\text{g}$
Volume of the solution $=1\text{L}$
Density of the solution $=1.392\text{g/mL}$ (given)
Mass of the solution $=1000\times 1.392=1392\text{g}$
Mass of water $=(1392-744)\text{g}=648\text{g}$
Moles of water $=\frac{648}{18}=36\text{mol}$
Total moles of ethylene glycol and water $=36+12=48\text{mol}$
Mole fraction og glycol $=\frac{12}{48}=0.25$