Q. Helium is added to the oxygen supply of deep sea divers because it is:
Answer: Less soluble in blood than nitrogen at high pressure
Notes: Deep-sea divers have their oxygen supply mixed with helium in order to avoid the toxic nature of oxygen under extreme pressures. The helium atom is much smaller than the nitrogen molecule, has a smaller electron cloud and is less polarizable. It, therefore, is less soluble in blood than nitrogen and prevents the formation of nitrogen bubbles in blood which blocks blood flow as the diver comes to the surface of the sea from underwater.