Ideal Gas Law Calculator

Calculate pressure (P), volume (V), moles (n), or temperature (T) using the ideal gas law PV = nRT. Includes combined gas law, Dalton's law, gas density, and molar mass calculations.

Ideal Gas Law: PV = nRT
Gas Constant (R): 0.08206 L·atm/(mol·K) = 8.314 J/(mol·K)
PV = nRT
STP: T = 273.15 K (0°C), P = 1 atm → V = 22.4 L/mol
Result
What Is the Ideal Gas Law?

The ideal gas law relates pressure (P), volume (V), moles (n), and temperature (T) of an ideal gas: PV = nRT, where R is the universal gas constant.

Key Concepts
  • R (gas constant): 0.08206 L·atm/(mol·K) or 8.314 J/(mol·K)
  • STP (Standard Temperature & Pressure): 273.15 K (0°C) and 1 atm
  • At STP: 1 mole of ideal gas = 22.4 L
  • Temperature must be in Kelvin for PV=nRT
Related Gas Laws
  • Boyle's Law: P₁V₁ = P₂V₂ (constant T and n)
  • Charles's Law: V₁/T₁ = V₂/T₂ (constant P and n)
  • Gay-Lussac's Law: P₁/T₁ = P₂/T₂ (constant V and n)
  • Combined Gas Law: P₁V₁/T₁ = P₂V₂/T₂ (constant n)
  • Avogadro's Law: V₁/n₁ = V₂/n₂ (constant P and T)
  • Dalton's Law: Ptotal = P₁ + P₂ + ... (partial pressures)
Worked Examples

1) Calculate volume at STP

Given: n = 2 mol, T = 273.15 K, P = 1 atm

V = nRT/P = (2)(0.08206)(273.15)/(1) = 44.8 L

2) Combined Gas Law

Initial: P₁ = 2 atm, V₁ = 5 L, T₁ = 300 K

Final: P₂ = 1 atm, T₂ = 273 K, V₂ = ?

V₂ = P₁V₁T₂/(P₂T₁) = (2)(5)(273)/((1)(300)) = 9.1 L

3) Dalton's Law

N₂ at 0.8 atm, O₂ at 0.2 atm

Ptotal = 0.8 + 0.2 = 1.0 atm

Unit Conversions
TypeConversions
Pressure1 atm = 101.325 kPa = 760 mmHg = 1.01325 bar = 14.696 psi
Volume1 L = 1000 mL = 0.001 m³ = 1000 cm³
TemperatureK = °C + 273.15; °F = (°C × 9/5) + 32

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