1. Rules for Balancing Equations Determine the correct formula for all reactants and products. Write the formulas for the reactants on the left side of arrow and the products on the right

2. Count the number of atoms on each side of the reaction. If a polyatomic ion appears unchanged on both sides count it as one unit. Balance the elements one at a time using coefficients. NEVER CHANGE SUBSCRIPTS TO BALANCE

3. Combination reactions Two or more substances come together to form a compound A + B  AB Mg + O 2  MgO

4. Combination Reactions 2 H 2 + O 2 => 2 H 2 O

5. Special combination reactions A metal oxide and water give a base A base is a compound with hydroxide K 2 O + H 2 O  KOH CuO + H 2 O  ? Right !! Copper(II) hydroxide

6. Special combination reactions A nonmetal oxide and water give an acid An acid is a compound with hydrogen SO 3 + H 2 O  H 2 SO 3 and/or H 2 SO 4 NO 2 + H 2 O  ? Right !! Nitric or nitrous acid

7. Important fact Combination reactions are responsible for acid rain. Sulfuric acid, nitric acid and carbonic acid are involved. What nonmetal oxides are involved? Where do they come from?

8. Decomposition reaction A substance breaks down forming two or more substances: AB  A + B NI 3 =  N 2 + I 2 MnO 2 H 2 O 2  H 2 O + O 2

9. Single replacement reactions A + BC  AC + B Aluminum + Iron(II) oxide  Aluminum oxide + Iron 2Al(s) Fe 2 O 3 (s) + --> Al 2 O 3 (s) + 2Fe(s)

10. Single replacement: will it or will it not happen? For metals, check the reactivity series A more reactive metal will “bump” a less reactive one Zn + HCl  ZnCl 2 + H 2

11. Single replacement: will it or will it not happen? Magnesium is placed in sulfuric acid Mg + H 2 SO 4  MgSO 4 + H 2 zinc is placed in phosphoric acid 3Zn + 2H 3 PO 4  Zn 3 (PO 4 ) 2 + 3H 2 Potassium is placed in contact with aluminum chloride 3K+ AlCl 3  3KCl + Al

12. Single replacement: will it or will it not happen? For non metals – look to the periodic table (as an activity series) F is more reactive than Cl F 2 + HCl  HF + Cl 2 But – Cl 2 + HF  no reaction

13. Write single replacement equations Magnesium is added to lead nitrate Iron is added to aluminum sulfide Sodium is added to calcium carbonate

14. Write single replacement equations Cl 2 + NaI => ? I 2 + NaCl => ? K + NaCl => ? At I Br Cl F Group VIIA

15. Double Replacement Two compounds interact The cations trade places AB + CD  AD +CB Na 3 PO 4 + FeCl 3  Fe 3 PO 4 + NaCl

16. What is the precipitate Silver nitrate and sodium hydroxide react: AgNO 3 + NaOH  NaNO 3 + AgOH

17. Check the solubility tables AlCl 3 + NaOH  Al(OH) 3 (s) + NaCl (aq) How do we know that the aluminum hydroxide is the precipitate? We look at a solubility table If the solubility table indicates “I” (insoluble), expect the substance to be a precipitate

18. Combustion reactions Fuel + oxygen gives carbondioxide, water, and energy C 3 H 8 (g) + 5O 2 (g) -----> 3CO 2 (g) + 4H 2 O (g) Fuels have carbon, hydrogen, and sometimes oxygen

19. Organic molecules: The alkanes C n H 2n+2 Methane CH 4 Ethane C 2 H 6 Propane C 3 H 8 Butane C 4 H 10 Pentane (five carbons) C 5 H 12 Hexane (six carbons) C 6 H 14 Heptane (seven carbons) C 7 H 16 Octane (eight carbons) C 8 H 18

20. Can you write balanced equations for the combustion of these hydrocarbons? Methane (one carbon) Ethane (two carbons) Propane (three carbons) Butane (four carbons) Pentane (five carbons) Hexane (six carbons) Heptane (seven carbons) Octane (eight carbons)