Question

Explain why the value of Tb is greater than that of Tb0.

Answer 1

what is Tb?

It is boiling point of the solution (pure solvent containing Solute)

and Tbo?

It is boiling point of pure solvent.

When a non volatile solute is added to volatile solvent, it's vapour pressure decreases, means you need to give more temperature to increase it's vapour pressure.

what is boiling temperature?

it is temperature at which the vapour pressure of solution equals the atmospheric pressure.

so,

When there is solute in the solvent, it's vapour pressure will be less, and you need more temperature to increase its vapour pressure and bring it to the atmospheric pressure compare to the pure Solvent.

hence boiling temperature of pure solvent is less than that of solute in solvent (solution).

hence,

Tb is greater than Tbo.