Henry's Law Calculator (Dissolved Gas, Fizzy Drinks, Aquariums)

What this tool does

Henry's law says the dissolved gas is proportional to the pressure of that gas above the liquid: double the pressure, double the gas. A fizzy drink is bottled under CO₂ at a few atmospheres; opening it drops the pressure to about 1 atm, and the surplus comes out as bubbles. The constant depends strongly on temperature, and warm liquids hold much less gas, so look it up at your temperature (for CO₂ in water at 25 °C, about 0.034 mol/(L·atm)). The law fails for gases that react with the liquid and at high pressures.

Formula

c = kH × p · gas released = kH (p − p₂) × R T ÷ p₂ (c in mol/L, p in atm, kH in mol/(L·atm))

Variables

Symbol	Meaning	Unit
`kh`	Henry's constant kH of the gas in that liquid	mol/(L·atm)
`p`	Pressure of the gas above the liquid	atm
`mw`	Molar mass of the gas	g/mol
`p2`	Pressure after opening	atm
`tc`	Temperature	°C
`C`	Dissolved gas	mol/L
`CG`	Dissolved gas by mass	g/L
`C2`	Dissolved gas at the new pressure	mol/L
`FR`	Share of the gas that comes out	%
`VG`	Gas released per litre of liquid, at the new pressure	L

Worked example

Henry's constant kH of the gas in that liquid0.034 mol/(L·atm)
Pressure of the gas above the liquid3 atm
Molar mass of the gas44.01 g/mol
Pressure after opening1 atm
Temperature25 °C

Dissolved gas0.1020 mol/L
Dissolved gas by mass4.489 g/L
Dissolved gas at the new pressure0.0340 mol/L
Share of the gas that comes out66.7 %
Gas released per litre of liquid, at the new pressure1.66 L

Limitations

The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
The default values are typical reference figures, not measurements of your situation. Replace them with your own data whenever you have it.