My question states: Given that the ground-level pressure of the Earth’s atmosphere is [tex]1.033 *10^5 N m^−^2,[/tex] calculate the mass of the atmosphere. If the ground-level atmospheric density is [tex]1.293 kg m^−^3[/tex], calculate the scale height. For the first bit, I used P=nKT, assuming a temperature of 300K, and I then calculated the number of molecules per unit area, and multiplied this number by the surface area of the Earth. I then assumed that the atmosphere was made entirely of Nitrogen and so multiplied the number of molecules by the mass of a molecule. I ended up with the answer [tex]5.99*10^1^4[/tex] kg. Does this sound about right? For the second part I am totally stumped. Surely if you put the height in as 0, that will tell you nothing about the scale height.