Ever wondered why water is taking longer to boil — well, this boiling point elevation calculator will assist you in the estimation of the boiling point elevation of a solution. The change in the boiling point of an impure solution depends on the molality of the solution and the ebullioscopic constant. Read on to understand what is boiling point elevation and how to estimate the boiling point elevation constant?

What is boiling point elevation?

The change or rise in the boiling point of a solution due to the addition of another compound or solute is known as boiling point elevation. This phenomenon occurs due to the dilution of pure solvent by adding or increasing the presence of a solute. The resultant solution now will have a boiling point higher than the pure solvent. For instance, adding salt to water will cause an elevation in the water or resultant solution's boiling point. Mathematically, this rise in the boiling point can be written using the boiling point elevation formula:

ΔT = i * Kb * m
…such that:
ΔT = Tsolution - Tsolvent

The terms m, Kb and i are; molality of solution, ebullioscopic constant or boiling point elevation constant and Van't Hoff factor respectively.

How to calculator boiling point elevation?

To calculate the boiling point elevation:

  1. Enter the boiling point of the pure solvent, Tsolvent.
  2. Insert the ebullioscopic constant or boiling point elevation constant, Kb.
  3. Fill in the molality of the solution, m.
  4. The calculator will estimate the boiling point elevation and the boiling point of the solution.

Note: The Van't Hoff factor is set to 1 as the default value and is present in the advanced mode of the calculator.

Example: Using the boiling point elevation calculator

Let's consider a case to estimate the water boiling point elevation as an example. Take the ebullioscopic constant of water as 0.512 and the molality of the solution as 3.

To calculate the boiling point elevation:

  1. Enter the boiling point of the pure solvent, Tsolvent = 100 °C.
  2. Insert the ebullioscopic constant or boiling point elevation constant, Kb = 0.512 °C⋅kg/mol.
  3. Fill in the molality of the solution, m = 3.
  4. Using the boiling point elevation equation:
    ΔT = i * Kb * m = 1 * 0.512 * 3 = 1.536 °C
    …and boiling point of the solution is:
    Tsolution = Tsolvent + ΔT = 100 + 1.536 = 101.536 °C

You can also use the advanced mode of the calculator, which has a direct option to pick a solvent and estimate the boiling point elevation.

Ebullioscopic constants

To use this calculator, you are going to need some ebullioscopic constants, here's a list of commonly available values to get you started.

Solvent
Ebullioscopic constant (in °C⋅kg/mol)
Water
0.512
Phenol
3.04
Acetic acid
3.07
Napthalene
5.8
Benzene
2.53

Van't Hoff factor

To use the advanced mode of the calculator, you need to learn about Van't Hoff factor. The Van't Hoff factor is defined as the ratio between particles produced due to dissolving a substance and the mass of the substance dissolved. Some common values of Van't Hoff factor are:

Solution
Van 't Hoff factor
Sugar in water
1
Sodium chloride (NaCl) in water
1.9 or 2
Calcium chloride(CaCl2) in water
2.9 or 3

FAQ

What do you mean by boiling point elevation?

The rise in the boiling point of a solution due to the addition of a solute is regarded as the boiling point elevation, such that the boiling point of the resultant solution is higher than the pure solvent.

How to estimate boiling point elevation?

To estimate boiling point elevation:

  1. Multiply the morality of the solution with the ebullioscopic constant of the solvent to obtain the change in temperature.
  2. Add the change in temperature to the boiling point of the pure solvent. Mathematically thats:
    ΔT = i * Kb * m
    where m, Kb and i are the molality of solution, ebullioscopic constant and Van't Hoff factor respectively.

What is the ebullioscopic constant of water?

The ebullioscopic constant for water is 0.512.

What is the ebullioscopic constant of benzene?

The ebullioscopic constant for benzene is 2.53.

Rahul Dhari
Boiling point of pure solvent (T_solvent)
°F
Ebullioscopic constant (K_b)
°C⋅
lb
/mol
Molality (m)
mol/
lb
Boiling point elevation (ΔT)
°F
Boiling point of solution (T_solution)
°F
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