November 30, 2015

Homework Help: Chemisty

Posted by Garcia on Thursday, November 1, 2012 at 9:05pm.

Enrico Fermi was a famous physicist who liked to pose what are now known as Fermi problems in which several assumptions are made in order to make a seemingly impossible estimate. One example of a Fermi problem is "Caesar's last breath" which estimates that you, right now, are breathing some of the molecules exhaled by Julius Caesar just before he died.

1. The gas molecules from Caesar's last breath are now evenly dispersed in the atmosphere.
2. The atmosphere is 50 km thick, has an average temperature of 15 C, and an average pressure of 0.20 atm.
3. The radius of the Earth is about 6400 km.
4. The volume of a single human breath is roughly 500 mL.

Perform the following calculations, reporting all answers to two significant figures.

Calculate the total volume of the atmosphere.

Calculate the total number of gas molecules in the atmosphere.

Calculate the number of gas molecules in Caesar's last breath (37C and 1.0 atm).

What fraction of all air molecules came from Caesar's last breath?

About how many molecules from Caesar's last breath do you inhale each time you breathe?

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