Henry's Law Calculator

Forcing Gas into Liquids

How do factories trap carbon dioxide gas inside a bottle of soda? They use Henry's Law.

Proposed by William Henry in 1803, the law states that the amount of gas that will dissolve into a liquid is directly proportional to the amount of pressure you apply to that gas above the liquid.

If you double the pressure of the gas pushing down on the liquid, exactly twice as many gas molecules will be forced to dissolve into the liquid.

The Chemistry of Carbonation

When a soda factory seals a bottle, they pump high-pressure $CO_2$ gas into the tiny airspace at the top of the bottle. This immense pressure forces the $CO_2$ molecules to crash into the liquid and dissolve.

When you unscrew the cap, you hear a "hiss" as the high-pressure gas escapes into the room. Because the pressure immediately drops, Henry's Law dictates that the concentration of dissolved gas must also drop. The $CO_2$ rapidly escapes the liquid in the form of bubbles!

The Equation

The Henry's Law constant ($k_H$) is unique for every specific gas-solvent combination. It also depends heavily on temperature (gases dissolve much better in cold liquids than in hot liquids).