Question

$138 \,g$ of ethyl alcohol is mixed with $72\, g$ of water. The ratio of mole fraction of alcohol to water is

• A. $ 3:4 $
• B. $ 1:2 $
• C. $ 1:4 $
• D. $ 1:1 $

Answer 1

Answer: (A)

Number of moles of $ {{C}_{2}}{{H}_{5}}OH=\frac{138}{46}=3 $
Number of moles of $ {{H}_{2}}O=\frac{72}{18}=4 $
Mole fraction, $ {{x}_{{{C}_{2}}{{H}_{5}}OH}}=\frac{3}{3+4} $
$ =\frac{3}{7} $
Mole fraction, $ {{x}_{{{H}_{2}}O}}=\frac{4}{3+7}=\frac{4}{7} $
$ \frac{{{x}_{{{C}_{2}}{{H}_{5}}OH}}}{{{x}_{{{H}_{2}}O}}}=\frac{3/7}{4/7}=\frac{3}{4} $