William Henry made systematic studies of the solubility of a gas in a liquid. He gave a quantitative relationship between the solubility of a gas in a solvent and pressure which is known as Henry’s law. The law states that- the mass of a gas dissolved per unit volume of the solvent at a constant temperature is directly proportional to the pressure of the gas in equilibrium with the solution.

If m is the mass of the gas dissolved in a unit volume of the solvent and p is the pressure of the gas in equilibrium with the solution, then

\[m \propto p\]

\[or,  m = K.p\]

where K is the proportionality constant. The magnitude of K depends on the nature of the gas, the nature of the solvent, the temperature and the units of pressure. Thus, Henry’s law may also be stated as: the solubility of a gas in a liquid at a particular temperature is directly proportional to the pressure of the gas in equilibrium with the solution.

When is Henry's law applicable?

Both A and B

The answer is 3 Both 1 and 2.

Henry's law states that the amount of a gas that dissolves in a liquid is directly proportional to the partial pressure of the gas above the liquid. This law only applies at a constant temperature and at a constant osmotic pressure.

If the temperature changes, the solubility of the gas will change. This is because the kinetic energy of the gas molecules will change, which will affect how likely they are to dissolve in the liquid.

If the osmotic pressure changes, the solubility of the gas will also change. This is because the osmotic pressure is a measure of the difference in solute concentrations between the two phases. If the osmotic pressure increases, the solute will be more likely to move from the liquid to the gas phase, which will decrease the solubility of the gas in the liquid.

So, Henry's law is only applicable when the temperature and osmotic pressure are constant. Option 1 and 2 are both necessary conditions for Henry's law to apply. Option 3 is the correct answer.