Colligative Properties

Step 1: Boiling point elevation formula.
The formula for boiling point elevation is: where is the change in boiling point, is the ebullioscopic constant (given as for benzene), and is the molality of the solution.

Step 2: Calculate the molality.
We are given that , and we know . Thus: Solving for :

Step 3: Calculate the molecular mass.
Molality is also defined as: Given that 10g of solute is dissolved in 100g (0.1 kg) of benzene, the number of moles of solute is: Now, the molecular mass of the solute is: Thus, the molecular mass is approximately .

Step 4: Conclusion.
The correct answer is option (1) .