A typical room is 3.5m long, 5.0m wide, and 2.0m high.
What is the total mass of the oxygen in the room assuming that the gas in the room is at STP and that air contains 21% oxygen and 79% nitrogen?

-Would somebody please just lead me through the steps on how to do this gas problem??
I would really appreciate it!(:

Question

A typical room is 3.5m  long, 5.0m  wide, and 2.0m  high.
What is the total mass of the oxygen in the room assuming that the gas in the room is at STP  and that air contains 21%  oxygen and 79%  nitrogen? 

-Would somebody please just lead me through the steps on how to do this gas problem??
I would really appreciate it!(:

aaronq · Answer

you would use PV=nRT, and find moles. After you convert to mass using $n=\dfrac{m}{M}$ (the molar mass (M) is given in the periodic table, make sure you use $O_2$ not just 1 oxygen). Standard conditions gives you P and T,  R is a constant. 

All you need is V. Draw the box, find the volume ($V_T=length*width*height)$ and find how much of that is just oxygen gas. $(V_{O_2}=0.21*V_T)$
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Plug into the PV=nRT equation and solve for n.