What is the total mass (in grams) of O2 in a room measuring 18.0 ft by 10.0 ft by 10.0 ft if the air in the room is at STP and the mole fraction of O2 is 0.2095?

Question

cuanchi · Answer

First you calculate the volume of the room by multiplying the 3 foots measurments.
 Then convert the volume from cubic foot to  liters. 
Then divide the liters by 22.4 that is the volume of one mole of any gas a STP and you will have the moles of O2 in the room. 
Finally multiply the number of moles by the molecular weight of the O2 (~32g/mol) and you will get the mass in grams of O2 in the room