Question

A mole of atoms is 6.02 x 10^23 atoms.To the nearest order of magnitude, how many moles of atoms are in a large domestic cat? The masses of a hydrogen atom,an oxygen atom,and a carbon atom are 1.0 u, 16 u, and 12 u, respectively. (Hint: Cats are about 10 kilograms in mass.)

Answer 1

This is an estimation problem.

The estimated composition of the cat is 65% C; 18.5% O and 9.5%H

So the gram formula weight is 0.65*12 + 0.185*32 + 0.095*1 = 13.8g/mole

Now an average cat has a mass of 10kg = 10000g

So an average cat should have 10000g/13.8g = 724.25 moles of atoms or around 725 moles which in order of magnitude is around 2 (Order of magnitude is basically the power of 10)

Now

if you wanted the order of magnitude of the number of atoms it would around 725*6.02x10^23= 4.3645*10^26 mole