#N_A# is simply another collective number like a dozen, or a gross, or a score. Admittedly, #N_A# is a VERY large number. We have #2.12xxN_A# molecules of propane, #H_3C-CH_2-CH_3#.
If we have this number of propane molecules, there are clearly #3xx2.12xxN_A# #"carbon atoms"#, and #8xx2.12xxN_A# #"hydrogen atoms"#. It would be worth your while to get your head around these quantities; they are simply NUMBERS.
#N_A# has the property that such a number of #""^1H# ATOMS a mass of #1# #g#, or such a number of #""^12C# atoms has a mass of #12# #g#. #N_A# is thus the link between atoms and molecules, about which we can only theorize, and the macro world or #g# and #kg# and #"litres"#, that which we can measure in the laboratory by mass or by volume. What is the mass of your quantity of propane molecules?
