Question

If air is 20% oxygen, how many moles of O2 are there in the room? How many molecules of O2?

Answer 1

To find out moles of O2 in the room we need to know volume of the room. 1 mole of O2 at STP occupies 22.4 liters. Assuming an imaginary room having volume of 1000 m³ (10×10×10 m)' will have volume =1000000 Liters.

So 20% of 1000 m^3 is 200 m^3 then volume of O2 in the room = 200000Liters.

Thus mole of O2 in the room = 2× 10^5 / 22.4 =8928.57 moles of O2.

1 mole of O2 contains 6.022× 10^23 number of molecules.

Thus the room contains = 6.022×10^23 × 8928.57 = 53767 × 10^23 molecules of O2.