Some Basic Concepts Of Chemistry Question 16
Question: Mole fraction of ethanol in ethanol water mixture is 0.25. Hence, the percentage concentration of ethanol by weight of mixture is
Options:
A) 25%
B) 75%
C) 46%
D) 54%
Show Answer
Answer:
Correct Answer: C
Solution:
$ {\chi_2}=\frac{n _2}{n _1+n _2}=0.25 $ (ethanol) (solute) $ (Mw _2=46g) $ $ {\chi_1}=\frac{n _1}{n _1+n _2}=0.75 $ (water) (solvent) $ (Mw _1=18g) $ $ \frac{{\chi_1}}{{\chi_2}}=\frac{n _1}{n _2}=\frac{3}{1}\Rightarrow \frac{W _1\times Mw _2}{Mw _1\times W _2}=\frac{3}{1} $ $ \frac{W _1\times 46}{18\times W _2}=3 $ $ \frac{W _1}{W _2}=1.17 $
$ \therefore $ $ \frac{W _2}{W _1+W _2}=0.46 $
