Caesar’s last breath. 

(a) How many molecules from Julius Caesar’s dying breath are currently in your lungs? The total mass of the Earth’s atmosphere is approximately 5 × 10¹⁸ kg, it is composed mainly of N₂ (78%) and O₂ (21%), and an average breath (called the tidal volume) is 1.5 L. 

(b) Is it possible that Caesar’s last breath would be evenly diffused around the globe by now? Many processes would distribute the molecules of his last breath, including convection, absorption and release in water, and diffusion. Calculate how far a nitrogen molecule will travel by the process of diffusion alone in the approximately 2000 years since Caesar’s demise. How much of a role does diffusion play in distributing and diluting emissions into the atmosphere?