Low oxygen concentration in the human body at high altitudes is due to the _____.
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → low atmospheric pressure
The amount of a gas that dissolves in a liquid depends on the partial pressure of the gas above it. This is Henry’s law: at a given temperature, the mole fraction of a gas in the solution is proportional to its partial pressure, \( p = K_H\,x \).
At high altitudes the low atmospheric pressure means a low partial pressure of oxygen, so by Henry’s law less oxygen dissolves in the blood.
Why the other options are incorrect
Option (1) Low temperature — Incorrect. Gases are more soluble at lower temperature, so cold air would, if anything, raise the dissolved oxygen; besides, body temperature stays the same.
Option (3) High atmospheric pressure — Incorrect. The pressure falls with height, and a higher pressure would increase the solubility of oxygen, not lower it.
NCERT (2026-27 edition):
Solubility of a Gas in a Liquid – …
