Dalton's Law Calculator
Calculate total pressure from partial pressures using Dalton's law: P_total = P1 + P2 + P3. Find partial pressure of any component in a gas mixture or from mole fraction.
Formula & Reference
| Variable | Symbol | Formula | Units |
|---|---|---|---|
| Dalton's Law Calculator | See formula | Pᵀᵒᵗₐₗ = ΣPᵢ | atm |
Step-by-Step Examples
Air: x(N₂)=0.78, x(O₂)=0.21, x(Ar)=0.01. Pᵀᵒᵗ=1.00 atm.
- P(N₂) = 0.78×1.00 = 0.78 atm
- P(O₂) = 0.21×1.00 = 0.21 atm
- P(Ar) = 0.01×1.00 = 0.01 atm
H₂ collected over water at 25°C. Pᵀᵒᵗ=745 mmHg, P(H₂O)=23.8 mmHg.
- P(H₂) = Pᵀᵒᵗ - P(H₂O) = 745-23.8
- P(H₂) = 721.2 mmHg
Total pressure 2.00 atm, 3 gases in equal mole fractions.
- Each mole fraction = 1/3 = 0.333
- Each partial pressure = 0.333×2.00 = 0.667 atm
Real-World Applications
Common Mistakes to Avoid
x₁ + x₂ + x₃ = 1.000. If using percentages (78%, 21%, 1%), convert to fractions first: 0.78, 0.21, 0.01.
Gas collected over water: P(gas) = P(total) - P(H₂O vapor). Water vapor pressure tables give P(H₂O) at each temperature.
Partial pressure = mole fraction × total pressure. Pᵢ = xᵢ × Pᵀᵒᵗ. Mole fractions always 0 to 1.
Frequently Asked Questions
Related Chemistry Calculators
Formula Explorer connections
Interpretation: This relationship connects pressure, volume, temperature, amount or phase composition for gases and volatile mixtures. Assumption: Use absolute temperature and compatible pressure-volume units. Ideal behavior weakens at high pressure, low temperature, strong intermolecular attraction or near phase change.