Vapor Pressure
| Formula / Notation | ln(P₂/P₁) = (ΔHvap/R)(1/T₁ - 1/T₂) |
|---|---|
| Also Known As | Equilibrium vapor pressure, saturation vapor pressure, SVP, partial pressure above liquid |
What is Vapor Pressure?
Vapor pressure is the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature. It reflects the tendency of a substance to evaporate. At the boiling point, vapor pressure equals atmospheric pressure. Vapor pressure increases with temperature (Clausius-Clapeyron equation). High vapor pressure = volatile substance = greater evaporation rate.
Formula & Notation
Other Names / Synonyms: Equilibrium vapor pressure, saturation vapor pressure, SVP, partial pressure above liquid
Properties & Characteristics
Uses & Applications
Safety Information
Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.
Key Facts
Frequently Asked Questions
Vapor pressure is the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature. It reflects the tendency of a substance to evaporate. At the boiling point, vapor pressure equals atmospheric pressure. Vapor pressure increases with temperature (Clausius-Clapeyron equation). High vapor pressure = volatile substance = greater evaporation rate.
Solvent selection (high VP → fast evaporation). Fire hazard assessment (high VP → more vapor). Storage container selection (sealed for high VP). Distillation design. Weather and atmospheric modeling. Environmental pollution (VOC emissions). Pharmaceutical inhaler design.
High vapor pressure compounds: greater inhalation exposure risk. Flammable solvents with high VP: serious fire/explosion hazard (diethyl ether VP = 530 mmHg). Mercury: low VP but toxic vapor. Vapor pressure data essential for industrial hygiene assessments.
The formula or notation for Vapor Pressure is: ln(P₂/P₁) = (ΔHvap/R)(1/T₁ - 1/T₂)