Account for the following:
Helium is used in diving apparatus.
Give reasons for the following :
Helium is used in diving apparatus as a diluent for oxygen.
Helium mixed with oxygen under pressure is given to sea-divers for respiration. Air is not given to sea-divers because nitrogen present in air being soluble in blood will give a painful sensation called bends by bubbling out blood on moving from high pressure(in deep sea) to the atmospheric pressure.
Air contains a large amount of nitrogen and the solubility of gases in liquids increases with increase in pressure. When sea divers dive deep into the sea, large amount of nitrogen dissolves in their blood. When they come back to the surface, solubility of nitrogen decreases and it separates from the blood and forms small air bubbles. This leads to a dangerous medical condition called bends. Therefore, air in oxygen cylinders used for diving is diluted with helium gas. This is done as He is sparingly less soluble in blood.