Question

If benzene in solution containing 30% by mass in carbon tetrachloride, calculate the mole fraction of benzene.

• (A)  0.412
• (B)  0.326
• (C)  0.529
• (D)  0.458

Answer 1

The Correct Option is D

Explanation:
Assume the mass of benzene be $30g$ in the total mass of the solution of $100g$. Mass of ${CCl}_4=(100-30)g$$=70g$Molar mass of benzene $\left(C_6{H}_6\right)=(6\times 12+6\times 1)g{mol}^{-1}$$=78g{mol}^{-1}$Therefore, Number of moles of $C_6{H}_6=\frac{\text{Mass}}{\text{Molar Mass}}$$=\frac{30}{78}mol$$=0.3846mol$Molar mass of $({CCl}_4)=(1\times 12+4\times 355)g{mol}^{-1}$$=154g{mol}^{-1}$Therefore, Number of moles of ${CCl}_4=\frac{\text{Mass}}{\text{Molar Mass}}$$=\frac{70}{154}mol$$=0.4545mol$Therefore, Mole fraction of benzene $=\frac{\text{ Number of moles of }{C}_6{H}_6}{\text{ Number of moles of }{C}_6{H}_6+\text{ Number of moles of }{CCl}_4}$$=\frac{0.3846}{0.3846+0.4545}$$=0.458$Hence, the correct option is (D).