1. Molar Mass & Percent Composition

2. The mass of 1 mole of an element or compound – The mass in grams from the Periodic Table Unit = grams per mole (g/mol)

3. Step One – Identify the molecular formula Ex: calcium fluoride Step Two – Determine the number of atoms of each element Ca = F = Step Three – Multiply the atomic mass by the number of atoms Ca = x = F = x = 78.08g/mol CaF 2 12 40.081 19.00238.00+

4. 1)PbCl 2 Pb = x = Cl = x = 2)Aluminum sulfate Al = S = O = g/mol + 207.21 35.45270.90 278.10 Al 2 (SO 4 ) 3 26.98x 2= 53.96 32.07x 3= 96.21 16.00x 12= 192.00+ 342.17g/mol

5. 3) Copper (II) chloride Cu = 63.55 x 1 = 63.55 Cl = 35.45 x 2 = 70.90 4) NH 4 Cl N = 14.01 x 1 = 14.01 H = 1.01 x 4 = 4.04 Cl = 35.45 x 1 = 35.45 g/mol + 134.45 CuCl 2 + 53.50g/mol

6. Step One – Identify the molecular formula Ex: iron (III) oxide Step Two – Calculate the molar mass of the compound Fe = 55.85 x 2 = 111.70 O = 16.00 x 3 = 48.00 Step Three – Divide the mass of the individual elements by the total, then multiply by 100 Fe = O = Fe 2 O 3 159.70 g/mol + 111.70 159.70 x 100 =69.9% 48.00 159.70 x 100 =30.1%

7. 1)H 2 O 2 H = 1.01 x 2 = 2.02 O = 16.00 x 2 = 32.00 2)Sn(OH) 4 Sn = 118.71 x 1 = 118.71 O = 16.00 x 4 = 64.00 H = 1.01 x 4 = 4.04 34.02 g/mol / 34.02x 100= 5.9 % / 34.02x 100 = 94.1 % 186.75 g/mol / 186.75x 100= 63.6 % / 186.75x 100= 34.3 % / 186.75x 100= 2.2 %