Elevation in Boiling Point - Practice Questions & MCQ

Elevation in Boiling Point:

Boiling Point: It is the temperature of a liquid at which its vapour pressure becomes equal to the atmospheric pressure. 

Now, the lowering of the vapour pressure of the solution occurs when the addition of non-volatile solute in solvent happens. In order to boil the solution, it is necessary to increase the temperature of the solution above the boiling point of the pure solvent. It means the boiling point of the solution is always higher than the boiling point of the pure solvent. This increase in the boiling point of the solution is called elevation in boiling point

• It is also termed as Ebullioscopy.

• Suppose  and  are the B.P. of pure solvent and solution respectively, then elevation in B.P  is given as 

 is directly proportional to the molality of solution

• If molality of the solution is one, then

• The elevation in B.P. is also given as
  

• Molecular weight of solute can be found out as follows
  

Here w = weight of solute

W = weight of solvent
K_b= molal elevation constant or ebullioscopic constant.
M = molar mass of solute

M₁ = molar mass of solvent

The value of or Ebullioscopic constant is a property of the solvent only and does not depend on the type of solute. The value of can be calculated as: 

Here L_v or = latent heat of vaporization.