CHAPTER+SIX+CHEMICAL+COMPOSITION>>>>

mass percent of element X=mass of X in a sample of the compound divided mass of the sample of the compound x 100 %
 * know how to convert between moles and number of atoms
 * know how to convet between grams and moles of an element
 * convert between grams and number of atoms
 * convert between grams and moles
 * convert between grams of a compound and number of molecules
 * convet between moles of a compound and moles of a constituent element
 * MASS PERCENT COMPOSITION OF COMPOUNDS**

//EMPIRICAL FORMULA// step one: if given %'s write down as grams step two: convert to moles step three: divide by smallest

//MOLECULAR FORMULA// molecular formula = empirical formula X n, where n = 1, 2, 3 .. n = molar mass divided by empirical formula mass for example if you go through a problem and find your empirical formula to be five carbon and four hydrogen you would first calculate the molar mass for that formula...which is 128.16 g/mol then you would calculate the empirical formula mass which is 64.09 g/mol and divide these two...this gives you 2. Multiple your original empirical formula by this number which gives you ten carbon and eight hydrogen...your molecular formula.

CHAPTER SEVEN CHEMICAL REACTIONS>>>