Henry's law is applicable for which scenario?

• A. Dilute gases in liquids
• B. Dense gases in liquids
• C. Solids in liquids
• D. Gases dissolved in solids

Answer: (A)

Henry's law describes how much gas dissolves in a liquid when temperature is fixed, and it states the dissolved amount is proportional to the gas’s partial pressure above the liquid. this proportionality holds best when the gas is present in dilute amounts, so the dissolved molecules don’t interact much with each other and the solvent–solute interactions stay roughly constant. in that dilute regime, the relationship is linear: the concentration of dissolved gas increases directly with the partial pressure, which is why dilute gases in liquids are the scenario where Henry’s law applies most reliably.

If the gas is dense in the liquid (higher partial pressure or stronger interactions), deviations from linearity occur because non-ideal behavior and interactions become important, so Henry’s law no longer describes the system well. Gases dissolved in solids or gases dissolved in solids involve different processes and laws, so Henry’s law isn’t the applicable description there.