2.  Shows the percent by mass of each element in a compound.

3.  Calculate the molar mass of the compound  Divide the total mass of each element by the molar mass of the compound and multiply by 100.

4.  What is the percent composition of Aluminum hydroxide? Al(OH) 3 1 Al @ 27.0 = 27.0 3 O @ 16.0 = 48.0 3 H @ 1.0 = 3.0 78.0 g/mol 27.0/78.0*100 = 34.6 % Al 48.0/78.0*100 = 61.5 % O 3.0/78.0*100 = 3.8 % H

5.  Calculate the percent composition of each of the following:  Tin IV sulfate 38.2 % Sn20.6 % S41.2 % O  Carbon tetrachloride 7.8 % C92.2 % Cl  Nitric acid 1.6 % H22.2 % N76.2 % O

6. The lowest whole number ratio of elements in a compound.

7.  Treat the compound as if it were 100 grams.  Convert each element to moles (don’t use diatomics because they are not alone).  Divide by the least number of moles.  If there is a decimal multiply all by the lowest whole number to get whole number.  These numbers are your subscripts in your empirical formula.

8.  What is the empirical formula of a compound that is 75% C and 25% H?

9.  What is the empirical formula of a substance that is 81.8% C and 18.2% H?  What is the empirical formula of a substance that is 82.76% C and 17.24% H?  What is the empirical formula of a substance that is 84.21% C and 15.79% H?  What is the empirical formula of a substance that is 66.67% C, 15.56% H, and 17.78% O?

10. Whole number multiple of the empirical formula showing the actual amount of atoms in a compound.

11.  Determine the empirical formula.  Calculate the molar mass of the empirical formula.  Divide the molar mass of the molecular formula (given) by the molar mass of the empirical formula.  Use this number as a multiplier for your empirical formula.

12. Example  A molecule is 75 % Carbon and 25 % Hydrogen with a molecular mass of 48 g/mol. What is the molecular formula?

13.  What is the molecular formula of a compound that is 54.54% Carbon, 9.09% Hydrogen, and 36.36% oxygen. The molar mass of the compound is 88 g/mol.

14.  What is the molecular formula of a compound that is 58.06% carbon, 19.35% hydrogen, and 22.58% nitrogen? The molar mass of the compound is 248 g/mole.