Consider the following statements about the solubility of gases in liquids and its effects.
(A) To avoid bends and the toxic effects of high concentrations of nitrogen in the blood, the tanks used by scuba divers are filled with air diluted with helium.
(B) When scuba divers come towards the surface, bubbles of oxygen are formed in the blood and block the capillaries.
(C) Low blood oxygen causes climbers at high altitudes to become weak and confused, a condition known as bends.
(D) Aquatic species are more comfortable in cold waters than in warm waters, as the solubility of gases in water increases with decrease of temperature.
Which of the statements given above are incorrect? Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (B) and (C) only
By Henry’s law, the solubility of a gas in a liquid is proportional to the partial pressure of the gas above it. A gas also dissolves less as the temperature rises. Each effect in the statements comes from a change in pressure or in temperature.
(A) To avoid bends and the toxic effects of high concentrations of nitrogen in the blood, the tanks used by scuba divers are filled with air diluted with helium. — Correct statement. The diluted air carries less nitrogen (11.7% helium, 56.2% nitrogen and 32.1% oxygen), so less nitrogen dissolves in the blood under high pressure.
(B) When scuba divers come towards the surface, bubbles of oxygen are formed in the blood and block the capillaries. — Incorrect statement. 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, not oxygen; this is the condition called bends.
(C) Low blood oxygen causes climbers at high altitudes to become weak and confused, a condition known as bends. — Incorrect statement. At high altitudes the partial pressure of oxygen is low, so less oxygen dissolves in the blood. This condition is anoxia; bends is the divers’ condition.
(D) Aquatic species are more comfortable in cold waters than in warm waters, as the solubility of gases in water increases with decrease of temperature. — Correct statement. Cold water holds more dissolved oxygen than warm water.
NCERT (2026-27 edition):
1.3.2 Solubility of a Gas in a Liquid – “• …When the divers come towards surface, the pressure gradually decreases. This releases the dissolved gases and leads to the formation of bubbles of nitrogen in the blood. This blocks capillaries and creates a medical condition known as bends, which are painful and dangerous to life.”
“To avoid bends, as well as, the toxic effects of high concentrations of nitrogen in the blood, the tanks used by scuba divers are filled with air diluted with helium (11.7% helium, 56.2% nitrogen and 32.1% oxygen).”
“• At high altitudes the partial pressure of oxygen is less than that at the ground level. This leads to low concentrations of oxygen in the blood and tissues of people living at high altitudes or climbers. Low blood oxygen causes climbers to become weak and unable to think clearly, symptoms of a condition known as anoxia.”
“…indicating that the solubility of gases increases with decrease of temperature. It is due to this reason that aquatic species are more comfortable in cold waters rather than in warm waters.”