Step 1: The law in words. Henry's law states that, at a given temperature, the mass of a gas dissolved in a fixed volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with the liquid.
Step 2: Equation and the constant. \(p = K_H x\), where \(p\) is the partial pressure of the gas, \(x\) is its mole fraction in solution, and \(K_H\) depends on the nature of the gas and temperature. Because the solubility of a gas falls as temperature rises, \(K_H\) increases with temperature.
Step 3: Where it is applied.
• Carbonated (fizzy) drinks are bottled under high CO2 pressure so that plenty of gas stays dissolved.
• The gas cylinders used by deep-sea divers contain helium-diluted air to stop large amounts of nitrogen from dissolving and later forming bubbles (decompression sickness).
• Since oxygen's partial pressure is low on high mountains, mountaineers suffer from anoxia because of poor oxygenation of the blood.