assume a diver breathes a mixture of Oxygen and Helium. by weight what ratio of helium to oxygen must be used if the diver is at an ocean depth of 50 meters?

Answer 1

The pressure of the gas in the lungs of the diver will be the same as the absolute pressure of the water at this depth of 50.0 meters. This is:
P = Po + ρgh = 101325 + 1000• 9.8•50 =591325 Pa = 5.84 atm
If the partial pressure due to the oxygen in the gas mixture is to be 1 atmosphere or less (or
approximately one-sixth of the total pressure), oxygen molecules should make up only about
one-sixth of the total number of molecules. This will be true if 1 mole of oxygen is used for
every 5 moles of helium. The ratio by weight is therefore
5 mol He•g/1 mol O2•g = 20•g/32•g = 0.625