Английская Википедия:Ebullioscopic constant
Шаблон:Short description Шаблон:Use American English Шаблон:More citations needed In thermodynamics, the ebullioscopic constant Шаблон:Math relates molality Шаблон:Mvar to boiling point elevation.[1] It is the ratio of the latter to the former:
- <math>\Delta T = iK_\text{b} b</math>
- Шаблон:Mvar is the van 't Hoff factor, the number of particles the solute splits into or forms when dissolved.
- Шаблон:Mvar is the molality of the solution.
A formula to compute the ebullioscopic constant is:[2]
- <math>K_\text{b} = \frac{RT_\text{b}^2 M}{\Delta H_\text{vap}}</math>
- Шаблон:Mvar is the ideal gas constant.
- Шаблон:Math is boiling point of the solvent.
- Шаблон:Mvar is the molar mass of the solvent.
- Шаблон:Math is the molar enthalpy of vaporization.
Through the procedure called ebullioscopy, a known constant can be used to calculate an unknown molar mass. The term ebullioscopy comes from the Latin language and means "boiling measurement". This is related to cryoscopy, which determines the same value from the cryoscopic constant (of freezing point depression).
This property of elevation of boiling point is a colligative property. It means that the property, in this case Шаблон:Math, depends on the number of particles dissolved into the solvent and not the nature of those particles.
Values for some solvents
| Solvent[3] | Шаблон:Math (in K⋅kg/mol) |
|---|---|
| Acetic acid | 3.08 |
| Benzene | 2.53 |
| Camphor | 5.95 |
| Carbon disulfide | 2.34 |
| Carbon tetrachloride | 5.03 |
| Chloroform | 3.63 |
| Cyclohexane | 2.79 |
| Diethyl ether | 2.02 |
| Ethanol | 1.07 |
| Water | 0.512 |
See also
- Ebullioscope
- List of boiling and freezing information of solvents
- Boiling-point elevation
- Colligative properties
References
External links
- ↑ Шаблон:Cite web
- ↑ Шаблон:Cite web
- ↑ P. W. Atkins, Physical Chemistry, 4th Ed., p. C17 (Table 7.2)
