Let's do some stoichiometry. Stoichiometry is about the conversion mathematical conversion between units in chemistry. The three units you usually come across are grans, moles, and atoms. Grams are measured in, well, grams. Atoms are the amount of atoms in a certain amount of a substance, and moles are wierd. Moles are the amount of grams it takes of a sumbtance to completely contain Avogadro's number, in atoms. A's number is 6.022E23, or 60,220,000,000,000,000,000,000. Since different atoms and molecules are larger than others, to find the molar mass of something, you must look at the Periodic table. The average atomic mass (that little number under their chemical symbol, Hydrogen's is 1.01, Carbon is 12.01, Oxygen is 16.00, etc) is the molar mass of elements. To find the molar mass of large, complex molecules, you add together all the atoms in the substance. For example, take sulfiric acid, or H2SO4. H2= 2.02 S= 32.07 O4= 64 64+32.07+2.02=98.09 Sulfiric acid's molar mass is 98.09 grams, which means that in order to contain A's number of sulfiric acid molecules, you need 98.09 grams. To find out how many molecules there are in a substance, given you know the amount of grams you have, you first divide the amount of grams you have by the molar mass of the substance to find out how many moles you have. You multiply this by A's number. For example, suppose you have 23.5g of sulfiric acid. 23.5g H2SO4 --------------- = 0.2395759mol (you have 98.09g H2SO4 this many moles) Next, 0.2395759×6.022E23= 1.442E23 atoms of H2SO4 Any questions?