Which of the following is NOT explained by Henry’s law?

The correct answer is Option (4) → Pure water is obtained from sea water by applying a pressure more than the osmotic pressure.

Henry’s law says that the solubility of a gas in a liquid is proportional to the partial pressure of the gas above it. It explains effects where a gas dissolves more at high pressure or less at low pressure.

Option (1) Bottles of soft drinks and soda water are sealed under high pressure. — Explained by Henry’s law. A high pressure of CO₂ makes more CO₂ dissolve in the drink.

Option (2) Scuba divers can suffer from bends when they come up towards the surface. — Explained by Henry’s law. Under water the high pressure dissolves more gas in the blood; as the pressure falls on rising, the gas comes out as bubbles of nitrogen that block capillaries.

Option (3) Climbers at high altitudes can suffer from anoxia. — Explained by Henry’s law. At high altitude the partial pressure of oxygen is lower, so less oxygen dissolves in the blood and tissues.

Option (4) Pure water is obtained from sea water by applying a pressure more than the osmotic pressure. — Not explained by Henry’s law. This is reverse osmosis, a colligative effect: the pressure pushes the solvent (water) out through a semipermeable membrane. No gas dissolving is involved.

NCERT (2026-27 edition):
1.6.5 Reverse Osmosis and Water Purification – “The direction of osmosis can be reversed if a pressure larger than the osmotic pressure is applied to the solution side. That is, now the pure solvent flows out of the solution through the semi permeable membrane. This phenomenon is called reverse osmosis and is of great practical utility. Reverse osmosis is used in desalination of sea water.”