1. Topic: Chemical Formulas Do Now: from last years regents

2. Chemical Formulas  Tell type & number atoms in compound Microscopic level: Formula gives atom ratios Microscopic level: Formula gives atom ratios Macroscopic level: Formula gives mole ratios Macroscopic level: Formula gives mole ratios

3. EXAMPLE 2H 2 O can mean 2H 2 O can mean 2 molecules of water 4 H atoms & 2 O atoms 4 H atoms & 2 O atoms 2 moles of water 4 moles of H atoms & 2 moles of O atoms 4 moles of H atoms & 2 moles of O atoms NOTE: WATER IS A BINARY COMPOUND – contains 2 elements only

4. What happens when a chemical formula contains  CuSO 4  5H 2 O  Means contains In this case it contains water so it’s called a hydrate

5. Types of formulas

6. Empirical Formula  Smallest whole # ratio of elements in compound CH 4 C 2 H 6 C 5 H 10

7. Molecular Formulas  Gives exact composition of molecule CH 4 C 2 H 6 C 5 H 10

8. Relationship between empirical and molecular formulas  molecular formula is whole number multiple of empirical formula  Molecular Formula = n (Empirical Formula) n (Empirical Formula) C 4 H 8 = 4(CH 2 ) C 4 H 8 = 4(CH 2 )

9. Ionic Compounds  Metal and Nonmetal  Their formulas are always empirical NaCl Fe 2 O 3

10. Covalent Molecules  Nonmetal only  Formulas can be empirical or molecular – need to know mass to determine CH 4 C 2 H 6 C 5 H 10

11. Say everything you can about: NaClC 6 H 6 C 6 H 12 O 6 CH 4 CF 4 BeSO 4 C 8 H 18 KIC 2 H 4 Cl 2 CaBr 2 CuSO 4  5H 2 O empirical Covalent, empir., molec? Covalent, molecular Ionic, empirical Covalent, molecular Covalent, empirical, molecular? Ionic, empirical Covalent, molecular Ionic, empirical Covalent, molecular

12. Lets practice- page 20

13. Molecular Formula  If know empirical formula and molar mass, can find molecular formula  Example: Find molecular formula for substance whose empirical formula is CH 2 and whose molar mass = 84.0 g Step 1: Find mass of empirical formula Step 2:Molar mass = whole # (n) Empirical mass Step 3: Multiply subscripts in empirical formula by n Step 1: C = 1 x 12 = 12 H = 2 x 1 = _2 14 g Step 2: 78g = 6 14g Step 3: 6 CH 2 = C 6 H 12