# Henry's Law Calculator

Free Henry's Law calculator. Calculate gas solubility in liquids using C = k_H × P. Includes constants for common gases in water.

## What this calculates

Calculate the solubility of a gas in a liquid using Henry's Law: C = k_H × P. The concentration of dissolved gas is directly proportional to the partial pressure of the gas above the solution.

## Inputs

- **Solve For** — options: Concentration (C), Partial Pressure (P), Henry's Law Constant (k_H) — Select what to calculate.
- **Concentration (C)** (mol/L) — min 0 — Concentration of dissolved gas in mol/L.
- **Partial Pressure (P)** (atm) — min 0 — Partial pressure of the gas above the solution.
- **Henry's Law Constant (k_H)** (mol/(L·atm)) — min 0 — Henry's law constant for the gas-solvent pair. CO₂ in water at 25°C: 0.034.
- **Common Gas (reference)** — options: Custom (enter k_H above), O₂ in water 25°C: k_H = 0.0013, CO₂ in water 25°C: k_H = 0.034, N₂ in water 25°C: k_H = 0.00061, H₂ in water 25°C: k_H = 0.00078, He in water 25°C: k_H = 0.00037 — Select a common gas for its Henry's law constant, or enter custom.

## Outputs

- **Result** — The calculated value.
- **Unit** — formatted as text — Unit of the result.
- **Formula** — formatted as text — Step-by-step calculation.

## Frequently Asked Questions

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

A: Henry's Law states that the amount of gas dissolved in a liquid is directly proportional to the partial pressure of the gas above the liquid. Mathematically: C = k_H × P, where k_H is Henry's law constant.

**Q: Why does soda go flat?**

A: Soda is carbonated under high CO₂ pressure. When you open the bottle, the pressure drops, and by Henry's Law, the CO₂ solubility decreases, causing the gas to escape as bubbles.

**Q: Does temperature affect Henry's Law constant?**

A: Yes. Henry's law constant generally decreases with increasing temperature, meaning gases become less soluble in warmer liquids. This is why warm soda goes flat faster than cold soda.

**Q: When does Henry's Law fail?**

A: Henry's Law fails at very high pressures, for gases that react with the solvent (like HCl in water), and for gases at high concentrations. It works best for dilute solutions of gases that do not react with the solvent.

---

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