# Julius ceasar's last breath .

• drchurch

#### drchurch

julius ceasar's last breath...

hey everyone, hope all is good. not with me, having trouble with a non assessed example in uni, any ideas anyone? :!)

## Homework Statement

make a fully reasoned order of magnitude estimate of the number of molecules from julius ceasar's last breath which were also present in your latest breath.

## Homework Equations

boltzmann equation. pressure equations

## The Attempt at a Solution

molecules in 1 breath, molecules in world, different pressures at different heights, intergrate pressure.

pretty stuck here would appreiciate any help!

cheers all

This is an order of magnitude estimate. Keep your model as simple as possible. I would base it only on the the first two numbers in your attempt.

do i not need to take into account the change in pressure in the Earth's atmosphere? simply ratioing the number of molecules in a breath of air to the number in the world seems a bit simple for ten marks?

cheers

How are you thinking change in pressure would matter?

I had a similar question about king arthurs cup and the water in it and the molecules of it going around in my body etc etc. what you have to do is estimate the volume of air in the Earth - forget about the fact that air thins with altitude, just improvise. then just use the fact that most air is nitrogen, so stick with calculating the number of nitrogen molecules in the world. you can look up how much volume on breath of air takes - its about half a litre. Then I'm sure i don't need to tell you the rest? ;) if it works out I am guessing there are roughly 10 molecules in your breath of caesers last breath - only a guess though

cheers vengeance, got it in the end, final equation something like 10E22/10E22 so 1 molecule, thanks for the advice tho dude