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Home  >>  JEEMAIN and AIPMT  >>  Chemistry  >>  Solutions
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What is the mole fraction of water in 20% w/w ethylene glycol solution?

$\begin{array}{1 1}(a)\;0.932&(b)\;0.068\\(c)\;0.102&(d)\;0.898\end{array}$

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1 Answer

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Answer: 0.932
Let's start with a 100g solution that contains 20% ethylene glycol, i.e, 20g and hence 100-20 = 80g of water.
Molar mass of ethylene glycol $ = 12 \times 2 + 1 \times 6 + 16 \times 2 = 62\; g\;mol^{-1}$
Number of moles of ethylene glycol $ = \large\frac{20}{62} $$= 0.322\; mol$
Since, the molar mass of water is known to be $18\;g\;mol^{-1}$, the number of moles of water $ = \large\frac{80}{18} $$= 4.44 \; mol$
$\Rightarrow $ Mole fraction of ethylene glycol $X_{C_2 H_6 O_2} = \large\frac{\text{moles of ethylene glycol}}{\text{moles of ethylene glycol + moles of water}}$
$\Rightarrow X_{C_2 H_6 O_2} = \large\frac{0.322}{0.322+4.44}$$ = 0.068$
Hence (a) is the correct answer.
$\Rightarrow X_{H_2O} = 1 - X_{C_2 H_6 O_2} = 1- 0.068 = 0.932$
answered Feb 12, 2014 by sreemathi.v
edited Jul 16, 2014 by balaji.thirumalai
 

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