The average breath inhales 0.5L of air. Assume all air particles have the same mass as an argon atom, 5*10^-26. The atmosphere is roughly 1% argon atoms.

1) How argon atoms does a person inhale with each breath? The density of air is 1.2 kg m^-3 (Note: there are 1000L in a m^3)

2) Estimate how many argon atoms passed through a person's lungs during their lifetime. The same atom was never breathed twice. He averaged 14 breaths per minute for the duration of his life - 85 years.

3) Estimate the total number of particles in the Earth's atmosphere. Do this by nothing that the surface air pressure of 10^5 Nm^-2 supports the weight of the atmosphere. Aussme that g does not vary over the height of the atmosphere. The radius of the Earth is 6.4*10^6m

4) Assume that the argon atoms the person in 2) breathed are now completely mixed throughout the Earth's atmosphere. Estimate how many of these you breathe in with each breath.
I have done some parts of it, but want to know what you guys get. I think i've mucked up some of the conversions