# Dalton's Law of Partial Pressures Calculator

Free Dalton's Law calculator. Calculate total pressure, partial pressures, and mole fractions for gas mixtures.

## What this calculates

Calculate total or partial pressures in gas mixtures using Dalton's Law: P_total = P₁ + P₂ + P₃ + ... Each gas contributes independently to the total pressure.

## Inputs

- **Solve For** — options: Total Pressure, Partial Pressure of a Gas, Mole Fraction — Select what to calculate.
- **Partial Pressure 1** (atm) — min 0 — Partial pressure of the first gas.
- **Partial Pressure 2** (atm) — min 0 — Partial pressure of the second gas.
- **Partial Pressure 3 (optional)** (atm) — min 0 — Partial pressure of the third gas (0 if only two gases).
- **Total Pressure** (atm) — min 0 — Total pressure of the gas mixture.
- **Mole Fraction** — min 0, max 1 — Mole fraction of the gas (for partial pressure calculation).

## Outputs

- **Result** — The calculated value.
- **Unit** — formatted as text — Unit of the result.
- **Calculation** — formatted as text — Step-by-step explanation.
- **Mole Fractions** — formatted as text — Mole fractions of each gas in the mixture.

## Frequently Asked Questions

**Q: What is Dalton's Law?**

A: Dalton's Law states that the total pressure of a gas mixture equals the sum of the partial pressures of each individual gas. Each gas behaves as if it alone occupies the entire volume.

**Q: What is a partial pressure?**

A: The partial pressure of a gas is the pressure it would exert if it alone occupied the container at the same temperature. It equals the mole fraction times the total pressure: P_i = x_i × P_total.

**Q: What is a mole fraction?**

A: The mole fraction (x) is the ratio of moles of one component to the total moles of all components. All mole fractions in a mixture sum to 1. x_i = n_i / n_total.

**Q: Does Dalton's Law apply to real gases?**

A: Dalton's Law works well for ideal gases and for real gases at low to moderate pressures. At very high pressures or for gases with strong intermolecular forces, deviations occur.

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Source: https://vastcalc.com/calculators/chemistry/daltons-law
Category: Chemistry
Last updated: 2026-04-21