Question

Why is it not advisable to carry oxygen cylinders by scuba divers mixed with nitrogen gas? Also, explain why helium gas is preferred to be mixed?

Answer 1

Hint: Water pressure is the consequence of the heaviness of all the water above pushing down on the water below. As you go further into the body of water, there is more water above, and subsequently, a more prominent weight pushing down. So, pressure increases with depth.

Complete answer:
Scuba divers rely on compacted air for their oxygen supply. The gas cylinders comprise oxygen, nitrogen and helium gas. Oxygen gas alone with nitrogen can't be utilized by the scuba divers since the intake of a high concentration of oxygen is harmful to our body. The high concentration of oxygen influences the central nervous system, lungs, and eyes. Nitrogen has some limitations and to overcome those limitations Helium is additionally utilized in those chambers.

As per Henry's law solubilities of gases increases with pressure. Accordingly both ${ N }_{ 2 }$ and ${ O }_{ 2 }$ will break up extensively in the blood and other body liquids. Oxygen is utilized for digestion, yet because of high lightweight and more prominent solubility ${ N }_{ 2 }$ will stay dissolved and will form bubbles when the diver goes to the air pressure. These bubbles affect nerve impulses and give rise to an illness called nitrogen narcosis. To avoid bends and to also avoid the harmful effects of the high concentration of nitrogen in the blood, the cylinders utilized by the divers are loaded up with air diluted with helium as it is lightweight and inert in nature. Helium is used as it is very little soluble in blood, also it reduces decompression and causes less discomfort to the diver in breathing.

Note: The possibility to make a mistake is that you may be confused as ${ N }_{ 2 }$ is somehow inert in nature but it's harmful to our central nervous system and lungs when used with oxygen for underwater scuba diving.