The percentage of the Group-18 gas in the tanks used by scuba divers is
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 11.7%
By Henry’s law, the solubility of a gas in a liquid is proportional to its partial pressure. Air breathed at high pressure under water puts more nitrogen into the blood, and the bubbles formed on coming up cause bends. So the tanks are filled with air diluted with helium, which is much less soluble in blood.
Helium is the Group-18 (noble) gas in the mixture, so its percentage is 11.7%.
NCERT (2026-27 edition):
Solubility of a Gas in a Liquid – …
