`DeltaT_b = K_b*n/M * i`

Enter a value for all fields

The Solvent Boiling Point Elevation calculator computes the change in the boiling temperature (ΔT_b) of a solvent based on the number of moles of solute (n), the mass of the solvent (M), the ebullioscopic constant (K_b) and the van't Hoff factor.

INSTRUCTIONS: Choose units and enter the following:

• (n) This is the number of moles of solute
• (M) This is the mass of the solvent
• (K_b)  This is the ebullioscopic constant in ^oC kg/mol
• (i) This is the van't Hoff factor

Boiling Point Elevation (ΔT_b):  The calculator returns the change in boiling point in degrees centigrade.   However, this can be automatically converted to other temperature units via the pull-down menu.

The Math / Science

The solvent boiling point elevation^[1] is a colligative property^[3] equation that calculates the new boiling temperature of the solvent after it has been mixed in with a solute. The addition of solutes causes the solvent to become impure, causing the boiling point to elevate. However, for the boiling point of the solvent to be raised, the solute must not contribute to the vapor pressure and must remain in the solvent throughout the phase change. The impurity of the solvent causes a decrease in it's chemical potential^[6], which is the amount of molar Gibbs free energy^[4],[5] one mole of solvent contributes to the mix. A high chemical potential drives the reaction towards product formation, however increasing solute molarity, increases boiling point and decreases chemical potential.

The formula for the change in boiling point of a solvent is:

               ΔTb = Kb • m • i

where:

• ΔT_b is the change in solvent boiling temperature of the solvent in units of (^oC). 
• K_b is the ebullioscopic constant, unique for each solvent in units of (^oC kg/mol), a full list can be found here.
• m is the solute molality in units of moles of solute per kg of solvent (mol/kg)
• i is the van't Hoff factor^[7] which takes dissociation of the solute in to account, for a solute that doesn't dissociate i=1, for dissociable solutes the value of i will depend on how many particle the solute dissociates in to, more information can be found here.

Related Topics

• Freezing point depression (for the Spanish site click here)
• Molality (for the Spanish site click here)
• Gibbs free energy (for the Spanish site click here)

Supplement Material

• Khan Academy:
  • Boiling point elevation
• HyperPhysics :
  • Boiling Point Elevation in Solutions 
  • Gibbs Free Energy and the Spontaneity of Chemical Reactions
• MIT:
  • Chemical Potential and Gibbs Distribution

References

[1]https://en.wikipedia.org/wiki/Boiling-point_elevation

[2]Whitten, et al. 10th Edition. Pp.524

[3]http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/collig.html

[4] https://en.wikipedia.org/wiki/Gibbs_free_energy

[5]http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/gibbspon.html

[6]https://en.wikipedia.org/wiki/Chemical_potential

[7]https://en.wikipedia.org/wiki/Van_%27t_Hoff_factor