Gas Mixture Partial Pressure Calculator
Calculate mole fractions and partial pressures for gas mixtures using Dalton's Law. Enter composition as moles, masses, or mole fractions.
Gas Mixture Partial Pressure Calculator
Describe a gas mixture by specifying its total pressure, temperature, volume, and the composition of each gas (moles, masses, or mole fractions). We'll estimate mole fractions and partial pressures for an ideal gas mixture.
Dalton's Law
Ptotal = Σ Pi
Total pressure equals sum of partial pressures
Mole Fraction
Pi = yi × Ptotal
Partial pressure proportional to mole fraction
Ideal Gas Law
PV = nRT
For the mixture and each component
Educational Only
Not for ventilation, safety, life-support, or industrial design purposes.
Understanding Gas Mixtures & Partial Pressures
Gas mixtures are fundamental in chemistry, biology, and engineering. Understanding how individual gas components contribute to total pressure is essential for many applications, from respiratory physiology to industrial gas processes.
Dalton's Law of Partial Pressures
The total pressure of a gas mixture equals the sum of the partial pressures of each component gas:
Each gas behaves independently as if it occupied the entire volume alone.
Mole Fraction & Partial Pressure
The partial pressure of a gas is proportional to its mole fraction in the mixture:
Where yi = ni / ntotal is the mole fraction (always between 0 and 1).
Key Equations
| Equation | Description | Variables |
|---|---|---|
| Pi = yi × Ptotal | Partial pressure from mole fraction | yi = mole fraction |
| yi = ni / ntotal | Mole fraction definition | n = moles |
| ni = mi / Mi | Moles from mass and molar mass | m = mass (g), M = molar mass (g/mol) |
| PV = nRT | Ideal gas law | R = 0.0821 L·atm/(mol·K) |
| Pi = niRT / V | Partial pressure from ideal gas law | For each component |
Example: Atmospheric Air
Dry air at sea level (Ptotal = 1 atm) contains approximately:
- 78.08% N₂ → PN₂ = 0.7808 atm
- 20.95% O₂ → PO₂ = 0.2095 atm
- 0.93% Ar → PAr = 0.0093 atm
- 0.04% CO₂ → PCO₂ = 0.0004 atm
Verification: 0.7808 + 0.2095 + 0.0093 + 0.0004 = 1.0000 atm ✓
Real-World Applications
Respiratory Physiology
Calculating oxygen and carbon dioxide partial pressures in alveoli and blood for understanding gas exchange.
Scuba Diving
Managing partial pressures of oxygen and nitrogen at depth to prevent oxygen toxicity and nitrogen narcosis.
Industrial Processes
Controlling gas mixtures in chemical reactors, such as the Haber process for ammonia synthesis.
Vapor-Liquid Equilibrium
Raoult's law relates partial pressures to liquid composition in distillation and evaporation.
Important Limitations
- Dalton's law assumes ideal gas behavior—real gases may deviate at high pressures or low temperatures
- This calculator is for educational purposes only
- Do NOT use for safety-critical applications like ventilation design, diving calculations, or industrial process control
- Real-world calculations require corrections for non-ideal behavior and should be performed by qualified professionals
Frequently Asked Questions
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