Question

The mole fraction of A in 10% (w/w) aq. solution of glucose is:

• A. $0.18$
• B. $0.011$
• C. $0.1$
• D. $0.017$

Answer 1

The correct option is B $0.011$

$10$% w/w solution of glucose in water means that 10 g of glucose is present in $100$ g of the solution i.e., $10$ g of glucose is present in $(100-10)g=90$ g of water.

Molar mass of glucose (C${}_6$H${}_{12}$O${}_6$) $=6\times 12+12\times 1+6\times 16=180$ gmol${}^{-1}$

Then, number of moles of glucose $=\frac{10}{180}$ mol

$=0.056$ mol

Number of moles of water $=\frac{90}{18}$ mol${}^{-1}=5$ mol

Mole fraction of glucose $\left(X\right)=\frac{0.056}{(0.056+5)}=0.011$

Hence, the correct option is $\text{B}$