Question: how many molecules are in the average room?
Answer: There are 6 x 10^23 particles in one mole of gas. Therefore, in 10,000 moles of air there will be 10,000 x 6 x 10^23 = 6 x 10^27 particles. Avogadro's constant and the amount of space a mole of gas takes up are fixed – so this answer is really dependent on how big your room is.