Rucete ✏ Chemistry In a Nutshell
1. Liquid-Vapor Equilibrium
- Vaporization (Evaporation & Boiling)
- Evaporation: Occurs below boiling point.
- Boiling: Occurs at or above boiling point.
- Condensation: Gas → Liquid.
- Dynamic Equilibrium:
- When rate of evaporation = rate of condensation.
- Equilibrium vapor pressure: Pressure at which equilibrium is reached.
- Higher temperature → Higher vapor pressure.
2. Heat of Vaporization & Boiling Point
- Molar Heat of Vaporization (ΔHvap)
- Energy required to vaporize 1 mole of liquid.
- Stronger intermolecular forces → Higher boiling point.
- Critical Point:
- Critical Temperature (Tc): Highest temperature where liquid exists.
- Critical Pressure (Pc): Highest pressure where liquid exists.
- Supercritical Fluid: Exists beyond critical temperature & pressure.
3. Liquid-Solid Equilibrium
- Melting & Freezing Points:
- Melting Point = Freezing Point (at equilibrium).
- Usually measured at 1 atm.
- Molar Heat of Fusion (ΔHfus):
- Energy needed to melt 1 mole of solid.
- Fusion energy < Vaporization energy because:
- Melting rearranges molecules, while vaporization completely separates molecules.
- Supercooling: Liquid is temporarily cooled below freezing point without solidifying.
4. Solid-Gas Equilibrium
- Sublimation: Solid → Gas (e.g., dry ice CO₂).
- Deposition: Gas → Solid (e.g., frost formation).
- Molar Heat of Sublimation (ΔHsub):
- Energy required to sublimate 1 mole of solid.
- ΔHsub = ΔHfus + ΔHvap (Sublimation = Melting + Vaporization).
In a nutshell
- Melting (Solid → Liquid) & Boiling (Liquid → Gas) require energy.
- Freezing (Liquid → Solid) & Deposition (Gas → Solid) release energy.
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Chemistry in a nutshell