2. Formula massMolar mass Units: amuUnits: grams/mole Sum of avg atomic masses of all atoms represented in the formula Numerically equal to the formula mass H = 1x2 O = 16 2+16 = 18 amu 2 + 16 = 18 g/mol

3.  Let’s start out with 14 g of NaCl 14 g of NaCl x 1 mole NaCl = 0.239 mol Na 58.5 g NaCl 0.239 mol NaCl x 6.02 E23 atom= 1.44 E23 1 mole NaCl

4.  The symbols for elements combined in a compound, with subscripts showing the smallest whole-number ratio of the different atoms in the compound.  Ex. Sugar (CH 2 O)

5.  Determine the empirical formula of the compound containing 17.15%C, 1.44% H and 81.41% F. Step 1 divide each % by the molar mass for the element Step 2 divide each by the smallest answer to get a whole number ratio

6.  The actual formula for a molecular compound.  x(empirical formula) = molecular formula X must be a whole number multiple X = molecular formula mass empirical formula mass

7.  Determine the molecular formula of a compound with an empirical formula of NH 2 and a formula mass of 32.06.

8.  Percent by mass of a certain element in a compound  (Mass of element/mass of compound) x 100  Ex. Water H = 1 x 2 = (2/18)x100 =11% O = (16/18)x100 = 89%