The relative lowering of vapour pressure of a solution containing a non-volatile, non-electrolyte solute in a solvent is 0.1 . The molar mass of the solvent is 50 ~g ~mol ⁻¹ and its boiling point elevation constant ( K_b ) is 4.5 ~K ~kg ~mol ⁻¹ . The elevation in boiling point of the solution is _ _ _ _ K. (Nearest integer)

Step-by-step solution

The relative lowering of vapour pressure is equal to the mole fraction of the solute. _ solute = 0.1 The mole fraction of the solvent is _ solvent = 1 - 0.1 = 0.9 The ratio of moles of solute to moles of solvent is: n_ solute n_ solvent = 0.1 0.9 = 1 9 Molality ( m ) is the number of moles of solute per kg of solvent: m = n_ solute n_ solvent M_ solvent ( in kg ) m = 1 9 0.050 = 1 0.45 = 20 9 ~mol ~kg ⁻¹ The elevation in boiling point is given by: T_b = K_b m T_b = 4.5 20 9 = 10 ~K Answer: 10