posted by steph .
A mixture of O2 and He is prepared for a scuba diver who is going to descend 200 ft below the ocean surface. At that depth, the diver breathes a gas mixture that has a total pressure of 7.00 atm. If the pressure of the O2 in the tank at 200 ft below the ocean surface is 1140 mmHg, what is the partial pressure of the He?
please help me i am completely lost
Ptotal = PHe + PO2.
Solve for PH3.