posted by Anonymous .
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?
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