Question 2 of 50beginner🔧 ApplyNumerical2 marks

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

Correct Answer

Mole fraction of benzene = 0.458

Exercise: Intext Questions | Q: 1.2 | (Page 5)
For More Understanding

Explanation

This is a straightforward mole fraction calculation. The key steps involve: (1) interpreting 30% by mass correctly, (2) calculating molar masses of both components, (3) finding moles of each component, and (4) applying the mole fraction formula. The context shows similar calculations in other examples where moles are calculated by dividing mass by molar mass, and mole fraction is found by dividing moles of one component by total moles.

Solution Steps

  1. Step 1: 30% by mass benzene means 30 g benzene and 70 g CCl₄ in 100 g solution.

  2. Step 2: Molar mass of benzene (C₆H₆) = 6×126 \times 12 + 6×16 \times 1 = 78 g mol⁻¹

  3. Step 3: Molar mass of CCl₄ = 12 + 4×35.54 \times 35.5 = 154 g mol⁻¹

  4. Step 4: Moles of benzene = 30 g / 78 g mol⁻¹ = 0.385 mol

  5. Step 5: Moles of CCl₄ = 70 g / 154 g mol⁻¹ = 0.455 mol

  6. Step 6: Total moles = 0.385 + 0.455 = 0.840 mol

  7. Step 7: Mole fraction of benzene = 0.385 / 0.840 = 0.458

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