Question

A solution contains 25% water, 25% ethanol and 50% ethanoic acid by mass. Calculate the mole fraction of each component in the same order.

• A. 0.301, 0.502, 0.196
• B. 0.502, 0.196, 0.301
• C. 0.245, 0.452, 0.502
• D. 0.502, 0.196, 0.452

Answer 1

Answer: (B)

Let the total mass of solution be 100 g.
So, mass of water, ethanol and ethanoic acid will be 25 g, 25 g, 50 g respectively.

$Numberofmoles=\frac{Mass\left(given\right)ofthecompound}{Molecularmassofthecompound}$

Moles of water = $\frac{25}{18}=1.389$
Moles of ethanol = $\frac{25}{46}=0.543$
Moles of ethanoic acid = $\frac{50}{60}=0.833$
Total moles = 1.389 + 0.543 + 0.833 = 2.765

$Molefraction=\frac{Molesofsolute}{Molesofsolvent+solute\left(Totalnumberofmoles\right)}$

Mole fraction of water = $\frac{1.389}{2.765}=0.502$
Mole fraction of ethanol $=\frac{0.543}{2.765}=0.196$
Mole fraction of ethanoic acid $=\frac{0.833}{2.765}=0.301$