Question

If the partial pressure of oxygen drops below 95.0 mmHg , passengers become drowsy. If this happens, oxygen masks are released. What is the total cabin pressure at which oxygen masks are dropped?An airplane is pressurized with air to 670 mmHg .Express your answer using two significant figures.

Ptotal =		mmHg

Answer 1

Percent of O2 in air = 21%

that is mole fraction of O2 in air = 21/100 = 0.21

Partial pressure of O2 = mole fraction of O2 x air pressure

                                = 0.21 x 670

                                = 140.7 mmHg

When pressure of O2 drops below 95 mmHg, O2 masks are released.

So,

Total cabin pressure = 95 x 670/140.7

                             = 452.38 mmHg

So the total cabin pressure for the partial pressure of O2 to be 95 mmHg and O2 masks to be dropped is 452.38 mmHg.

P(total) = 452.38 mmHg