1. Unit Nine: Chemical Reactions chemical reactions

2. Timely news related to chemistry: This is just one reason why understanding some chemistry is important to our daily lives. Ferric chloride (FeCl 3 ) Nitric Acid (HNO 3 ) Both are corrosive materials used to etch metal. Chemistry in the news: explosion in Spain

3. Chemical Reactions: A chemical reaction is the process by which one or more substances are changed into one or more different substances. In a chemical reaction, the original substances are called the reactant and the resulting substances are called the product. A chemical reaction is described by chemical equations. Basic Structure of a chemical reaction: Reactants  Products

4. Interpreting Chemical Equations: Chemical reactions can be written as word equations or as formula equations. Underline the reactant(s) and circle the product(s) in the following examples: Iron reacts with oxygen to produce iron oxide (rust).(Word equation) 2Fe(s) + O 2 (g)  FeO(s)(Formula equation

5. Iron reacts with oxygen to produce iron oxide (rust). (Word equation) 2Fe(s) + O 2 (g)  FeO(s) (Formula equation)

6. Observations about writing chemical reaction: 1.The reactants are always written to the left of the yield arrow (  ) and the products are always written to the right. 2.Chemical formulas are still written using the criss-cross method. 3.Formula equations are balanced using coefficients which are written in front of the chemical formula.

7. Symbols and Chemical Equations:  Yield arrow (s)solid (l)liquid (g)gas (aq)Aqueous: water solution

8. Reactant(s)  Products Pb(NO 3 ) 2 (aq) + KI (aq)  PbI 2 (s) + 2KNO 3 (aq) Lead iodide: ____________Potassium nitrate: ________ Potassium iodide: ________Lead nitrate : ___________

9. Pb (NO 3 ) 2 (aq) + KI (aq)  PbI 2 (s) + 2KNO 3 (aq) Lead iodide: ProductPotassium nitrate: Product Potassium iodide: ReactantLead nitrate : Reactant

10. Recognizing types of reactions: There are five types of reaction that fit the following patterns: 1.Synthesis A + B  AB 2.DecompositionAB  A + B 3.Single replacementA + BC  AC + B 4.Double replacementAB + CD  AD + CB 5.Combustion: C x H y + O 2  CO 2 + H 2 O

11. Types of reactions Pb(NO 3 ) 2 (aq) + KI (aq)  PbI 2 (s) + 2KNO 3 (aq) AB + CD  AD + CB Double replacement!

12. Writing Chemical Reaction: Reactants : Lead(II) nitrate (aq) + Potassium iodide Products: Lead(II) iodide + Potassium nitrate Pb (NO 3 ) 2 (aq) + KI (aq)  ____________ + 2KNO 3 (aq) Your job: determine the formula and state of Lead (II) iodide Pb 2+ = ________ I - = ___________ Formula = ____________

13. Balancing Chemical Reactions: Since matter is neither created nor destroyed during a chemical reaction (Law of Conservation of Mass), it is necessary to balance the elements in a chemical equation. This is done using coefficients. Coefficients do not change the chemical formula but the do change the amount of each substance.

14. Coefficients & Counting! Remember this? 3H 2 O = ____ H, _____ O 2Al 2 (SO 4 ) 3 = ______ Al, _____S, ____ O

15. Answers 3H 2 O = 6 H, 3 O 2Al 2 (SO 4 ) 3 = 4 Al, 6 S, 24 O