thermodynamics Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed by the four laws of the ...

, the ebullioscopic constant relates

molality Molality is a measure of the number of moles of solute in a solution corresponding to 1 kg or 1000 g of solvent. This contrasts with the definition of molarity which is based on a specified volume of solution. A commonly used unit for molali ...

boiling point elevation Boiling-point elevation describes the phenomenon that the boiling point of a liquid (a solvent) will be higher when another compound is added, meaning that a solution has a higher boiling point than a pure solvent. This happens whenever a non-volat ...

. It is the ratio of the latter to the former: :

\Delta T = iK_\text b

* is the

van 't Hoff factor The van 't Hoff factor (named after Dutch chemist Jacobus Henricus van 't Hoff) is a measure of the effect of a solute on colligative properties such as osmotic pressure, relative lowering in vapor pressure, boiling-point elevation and freez ...

, the number of particles the solute splits into or forms when dissolved. * is the

of the solution. A formula to compute the ebullioscopic constant is: :

K_\text = \frac

* is the

ideal gas constant The molar gas constant (also known as the gas constant, universal gas constant, or ideal gas constant) is denoted by the symbol or . It is the molar equivalent to the Boltzmann constant, expressed in units of energy per temperature increment per ...

. * is

boiling point The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the surrounding envir ...

of the

solvent A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...

. * is the

molar mass In chemistry, the molar mass of a chemical compound is defined as the mass of a sample of that compound divided by the amount of substance which is the number of moles in that sample, measured in moles. The molar mass is a bulk, not molecular, p ...

of the solvent. * is the molar

enthalpy of vaporization The enthalpy of vaporization (symbol ), also known as the (latent) heat of vaporization or heat of evaporation, is the amount of energy (enthalpy) that must be added to a liquid substance to transform a quantity of that substance into a gas. T ...

. Through the procedure called

ebullioscopy An ebullioscope (from the Latin ''ēbullīre'' (to boil) + -scope) is an instrument for measuring the boiling point of a liquid. This can be used for determining the alcoholic strength of a mixture, or for determining the molecular weight of a non- ...

, a known constant can be used to calculate an unknown

. The term ''ebullioscopy'' comes from the

Latin language Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...

and means "boiling measurement". This is related to

cryoscopy Freezing-point depression is a drop in the minimum temperature at which a substance freezes, caused when a smaller amount of another, non- volatile substance is added. Examples include adding salt into water (used in ice cream makers and for ...

, which determines the same value from the

cryoscopic constant In thermodynamics, the cryoscopic constant, , relates molality to freezing point depression (which is a colligative property). It is the ratio of the latter to the former: :\Delta T_f = -i \cdot K_f \cdot b * is the van ‘t Hoff factor, the ...

(of

freezing point depression Freezing-point depression is a drop in the minimum temperature at which a substance freezing, freezes, caused when a smaller amount of another, non-Volatility (chemistry), volatile substance is added. Examples include adding salt into water (u ...

). This property of elevation of boiling point is a colligative property. It means that the property, in this case , depends on the number of particles dissolved into the solvent and not the nature of those particles.

Values for some solvents

References

External links

Ebullioscopic constant calculator
AD Phase transitions {{Thermodynamics-stub

Values for some solvents

See also

References

External links