G

Gay-Lussac's Law

P/T = k (constant V, n); P₁/T₁ = P₂/T₂
Quick Reference
Formula / NotationP/T = k (constant V, n); P₁/T₁ = P₂/T₂
Also Known AsPressure-temperature law, Amontons' law, isochoric (constant volume) gas law

What is Gay-Lussac's Law?

The law stating that the pressure of a fixed amount of gas at constant volume is directly proportional to its absolute temperature (P ∝ T). Also refers to the law of combining volumes: gases react in simple whole-number ratios by volume at the same temperature and pressure.

Formula & Notation

P/T = k (constant V, n); P₁/T₁ = P₂/T₂

Other Names / Synonyms: Pressure-temperature law, Amontons' law, isochoric (constant volume) gas law

Properties & Characteristics

Gay-Lussac's law (or Amontons' law) states that the pressure of a fixed amount of gas at constant volume is directly proportional to its absolute temperature (in Kelvin): P ∝ T, or P/T = constant. It was described by Guillaume Amontons (1702) and later by Joseph Gay-Lussac (1809). Graphically, P vs T (in Kelvin) is a straight line passing through the origin for an ideal gas. It forms one component of the combined gas law.

Uses & Applications

Gay-Lussac's law explains why pressure in a sealed, rigid container (autoclave, pressure cooker, gas cylinder) rises when heated. It is used to calculate the pressure increase in sealed gas storage vessels when temperature rises, and in the design of pressure relief valves for safety.

Safety Information

The direct proportionality of pressure and temperature means that gas cylinders stored in hot environments (car boots, direct sunlight) experience pressure increases that can exceed valve safety limits and cause rupture or explosion. Always store gas cylinders at <50°C and away from heat sources.

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

Key Facts

Term Gay-Lussac's Law
Formula P/T = k (constant V, n); P₁/T₁ = P₂/T₂
Synonyms Pressure-temperature law, Amontons' law, isochoric (constant volume) gas law

Frequently Asked Questions

The law stating that the pressure of a fixed amount of gas at constant volume is directly proportional to its absolute temperature (P ∝ T). Also refers to the law of combining volumes: gases react in simple whole-number ratios by volume at the same temperature and pressure.

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