Question

The molarity of an aqueous solution of glycol is 12 M. The density of the solution is 1.392 g/mL. Find the mole fraction of glycol.
(given, molar mass of glycol = 62 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 = $12M$
Assuming 1 litre of the solution,
Moles of glycol = $12mol$
Molar mass of glycol = $62g/mol$ (given)
Mass of glycol = $62\times 12=744g$
Volume of the solution = 1 L
Density of the solution = 1.392 g/mL (given)
Mass of the solution =$1000\times 1.392=1392g$
Mass of water = $(1392-744)g=648g$
Moles of water = $\frac{648}{18}=36mol$
Total moles of glycol and water = $36+12=48mol$
Mole fraction = $\frac{12}{48}=0.25$