C

Critical Pressure

Quick Reference
Also Known AsP_c, critical pressure of a gas, thermodynamic critical pressure

What is Critical Pressure?

Critical pressure is the minimum pressure required to liquefy a gas at its critical temperature. Above the critical temperature, no amount of pressure can liquefy the gas. Critical pressures vary widely between substances: CO₂ has Pc = 73.8 bar, while water has Pc = 220.9 bar. Knowledge of critical pressure is essential in supercritical fluid technology.

Properties & Characteristics

Critical pressure (P_c) is the minimum pressure required to liquefy a gas at its critical temperature. Above the critical pressure and critical temperature, a substance is a supercritical fluid. Critical pressures vary widely: CO₂ = 73.8 atm, H₂O = 220.6 atm, He = 2.27 atm. The van der Waals equation provides an approximation: P_c = a/(27b²).

Uses & Applications

Critical pressure data is essential for designing high-pressure equipment, supercritical fluid processes (extraction, chromatography), and thermodynamic modelling. Knowledge of P_c guides pipeline design for natural gas and CO₂ transport in carbon capture and storage systems.

Safety Information

All equipment designed to operate at or above critical pressures must be rated accordingly. Critical pressure for water (220 atm) requires supercritical water oxidation (SCWO) reactors to be heavily engineered pressure vessels with appropriate safety systems.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Critical Pressure
Synonyms P_c, critical pressure of a gas, thermodynamic critical pressure

Frequently Asked Questions

Critical pressure is the minimum pressure required to liquefy a gas at its critical temperature. Above the critical temperature, no amount of pressure can liquefy the gas. Critical pressures vary widely between substances: CO₂ has Pc = 73.8 bar, while water has Pc = 220.9 bar. Knowledge of critical pressure is essential in supercritical fluid technology.

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