Question

Assertion: Helium is used in diving apparatus.
Reason: Solubility of helium is less in blood.
Choose the correct options.
A. Both Assertion and Reason are correct but Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
C. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrect

Answer 1

H\int: Helium is an inert gas. Check the properties of gases required in diving apparatus. Solubility means dissolution of solutes in solvent. Diving is done under water, underwater pressure decreases. So, oxygen is required to breathe.

Complete step by step answer:
Let us first see the conditions on gas mixtures to be used in diving apparatus.
(1) The mixture should not become toxic when being breathed at high pressure that's when underwater. Like, oxygen and nitrogen are the gases that become toxic under pressure.
(2) It should not contain harmful contaminants. Carbon dioxide and carbon monoxide are common gases which may contaminate the breathing gases.
(3) It should contain sufficient oxygen to support life and consciousness.
Then, the gaseous mixture that can be used is helium in the sea diving breathing mix (Heliox, 0% ${{\text{N}}_{2}}$) is to reduce the amount of nitrogen and oxygen (Nitrox) in a standard mixture. This is because the lower amount of nitrogen reduces the chances of ‘nitrogen narcosis’ in deep diving and this also the lower proportion of oxygen. So, the assertion is correct.
The less percentage of nitrogen $\left( {{\text{N}}_{2}} \right)$ is used to that of helium $\left( \text{He} \right)$ in gaseous mixture because the solubility of helium is less than that of nitrogen. Thus, it diffuses more rapidly. The elimination of inert gases from blood would be more rapid than nitrogen. Moreover, nitrogen has high partial pressure, nitrogen gas $\left( {{\text{N}}_{2}} \right)$ gets dissolved in blood to form bubbles or decompression sickness. So, the reason is correct.

The correct answer of this question is option ‘a’, Both Assertion and Reason are correct but Reason is the correct explanation for Assertion.

Note: There are many other mixtures of gases used by divers:
(1) In technical diving and commercial diving, Trimix is a mixture of oxygen, nitrogen and helium instead of air to avoid the dangers of oxygen toxicity.
(2) A gas mixture of hydrogen and oxygen named Hydrox is used in very deep diving as a breathing gas.