Now N_A=6.022xx10^23*"molecules". This specifies a molar quantity of stuff. By definition N_A ""^12C ATOMS has a mass of 12.00*g, and constitutes a molar quantity. The "mole" is thus the link between the sub-micro world of atoms and molecules, which we cannot see but whose existence we can infer, to the macro world of "grams", and "litres", that which we can measure out on a balance or measure volumetrically.
Molar masses are conveniently printed on the Periodic Table. You will not have to remember the masses, but you will have to use the Periodic Table to express molar masses of different compounds. Molar quantities of carbon and oxygen atoms have masses of 12*g, and 16*g respectively. You have 44.0*g of carbon dioxide. It does not take too much arithmetic to work out that such a mass represents a molar quantity of carbon dioxide molecules...........
And thus there are 6.022xx10^23 individual carbon dioxide molecules (or N_A such "mollykewels"). In this quantity, can you tell how many carbon and oxygen atoms there are?
