10g of a non-volatile and non-dissociating solute is dissolved in 200g of benzene. The resulting solution boils At temperature of 81.20oC. Find the molar mass of solute.
Given that the BP of pure benzene is 80.10oC and Its elevation boiling point constant = 2.53 oC/m.

The molar mass of solute is 115 g/mol.

Explanation:

Elevation in the boiling point is defined as the difference between the boiling point of the solution and the boiling point of the pure solvent.

The expression for the calculation of elevation in boiling point is:

OR

......(1)

where,

Boiling point of pure solvent (benzene) =

Boiling point of solution =

i = Vant Hoff factor = 1 (for non-electrolytes)

= Boiling point elevation constant =

= Given mass of solute = 10 g

= Molar mass of solute = ? g/mol

= Mass of solvent = 200 g

Putting values in equation 1, we get:

Hence, the molar mass of solute is 115 g/mol.

im not exactly sure but i think its b!