What is the total mass (in grams) of O2 in a room measuring (20.0 5.0 11.0) ft3 if the air in the room is at STP and contains 20.95% O2?

Answer 1

Change 20 ft, 5.0 ft, and 11.0 ft to cm, then length x width x height = volume in cubic centimeters (cc) and change that to liters.
32 g x (volume room in L/22.4) = grams if pure oxygen.
Multiply that by 0.2095.