He partial pressure of oxygen gas in our atmosphere is 0.21 atm. this is the partial pressure at which human lungs have evolved to be able to breathe this gas. a scuba diver, will thus still have to breath oxygen at this pressure even when diving way down in the water. if a mixture of helium and oxygen (heliox) in his tank is at a pressure of 8.30 atm, what must the partial pressure be of helium to keep the partial pressure of oxygen at 0.21 atm?

Hello!

The partial pressure of helium to keep the partial pressure of oxygen at 0,21 atm in a scuba-diver tank is 8,09 atm

To solve this question, we can use the Dalton's Law, which states that the total pressure in a container with a mixture of gases is the sum of the partial pressures o each individual gas. For the case of this mixture the Dalton's Law is as follows:



In this equation, we need to clear for PHe, knowing that the PO₂ should be 0,21 atm, to find the required pressure of Helium:



Have a nice day!

It shows that the experiment is designed properly.