Practicing Success

Target Exam

CUET

Subject

Chemistry

Chapter

Physical: Solutions

Question:

Calculate the mole fraction of benzene in solution containing 30% by mass in carbon tetrachloride?

Molar mass of benzene = 78 g /mol ; Molar mass of carbon tetrachloride = 154 g/mol

Options:

0.384

0.4545

0.5

0.458

Correct Answer:

0.458

Explanation:

Assume that the mass of benzene be 30g in the total mass of the solution of 100g.

Then mass of CCl4 = 100g - 30g = 70g

Number of moles of benzene = \(\frac{mass}{\text{molar mass}}\)

                                          = \(\frac{30g}{78g mol^{-1}}\)

                                          = 0.3846 mol

Number of moles of CCl4 = \(\frac{mass}{\text{molar mass}}\)

                                          = \(\frac{70g}{154 gmol^{-1}}\)

                                          = 0.4545 mol

Therefore mole fraction of benzene = \(\frac{\text{Number of moles of benzene}}{\text{ Number of moles of benzene+ Number of moles of CCl4}}\)

                                                   = \(\frac{0.3846}{0.3846 + 0.4545}\)

                                                   = 0.458