1. Chemical Reactions reactants  products Balancing chemical equations Types of chemical reactions

2. How reactants are transformed into products? Reactants are transformed during chemical reactions Energy is required (absorbed) to break a chemical bond Energy is released when a chemical bond forms

3. Balancing equations Obey law of conservation of matter Chemical equations have two parts: reactants and products

4. How to balance? The total number of atoms of each element should be the same on both sides of equation Use coefficients to balance equations Example: 2H 2 + O 2  2 H 2 O

5. Types of chemical reactions Single replacement Double replacement Decomposition Combination Combustion

6. Synthesis (Combination) Reactions Two or more substances combine to form a new compound. A + X  AX  Reaction of elements with oxygen and sulfur  Reactions of metals with Halogens  Synthesis Reactions with Oxides  There are others not covered here!

7. Decomposition Reactions A single compound undergoes a reaction that produces two or more simpler substances Decomposition of: Binary compounds 2H 2 O( l )  2H 2 (g) + O 2 (g) Metal carbonates CaCO 3 (s)  CaO(s) + CO 2 (g) Metal hydroxides Ca(OH) 2 (s)  CaO(s) + H 2 O(g) Metal chlorates 2KClO 3 (s)  2KCl(s) + 3O 2 (g) Oxyacids H 2 CO 3 (aq)  CO 2 (g) + H 2 O( l ) AX  A + X

8. Single Replacement Reactions Replacement of:  Metals by another metal  Hydrogen in water by a metal  Hydrogen in an acid by a metal  Halogens by more active halogens A + BX  AX + B BX + Y  BY + X

9. The Activity Series of the Metals Lithium Potassium Calcium Sodium Magnesium Aluminum Zinc Chromium Iron Nickel Lead Hydrogen Bismuth Copper Mercury Silver Platinum Gold Metals can replace other metals provided that they are above the metal that they are trying to replace. Metals above hydrogen can replace hydrogen in acids. Metals from sodium upward can replace hydrogen in water

10. Single Replacement Reactions Sodium chloride solid reacts with fluorine gas NaCl (s) + F 2(g)  NaF (s) + Cl 2(g) Note that fluorine replaces chlorine in the compound Aluminum metal reacts with aqueous copper (II) nitrate Al (s) + Cu(NO 3 ) 2(aq)  Cu (s) + Al(NO 3 ) 3(aq) 22 23 32

11. The Activity Series of the Halogens Fluorine Chlorine Bromine Iodine Halogens can replace other halogens in compounds, provided that they are above the halogen that they are trying to replace. 2NaCl(s) + F 2 (g)  2NaF(s) + Cl 2 (g) MgCl 2 (s) + Br 2 (g)  ???No Reaction ???

12. Double Replacement Reactions The ions of two compounds exchange places in an aqueous solution to form two new compounds. AX + BY  AY + BX One of the compounds formed is usually a precipitate, an insoluble gas that bubbles out of solution, or a molecular compound, usually water.

13. Double Replacement Reactions Think about it like “foil”ing in algebra, first and last ions go together + inside ions go together Example: AgNO 3(aq) + NaCl (s)  AgCl (s) + NaNO 3(aq) Another example: K 2 SO 4(aq) + Ba(NO 3 ) 2(aq)  KNO 3(aq) + BaSO 4(s) 2

14. Combustion Reactions A substance combines with oxygen, releasing a large amount of energy in the form of light and heat. Reactive elements combine with oxygen P 4 (s) + 5O 2 (g)  P 4 O 10 (s) (This is also a synthesis reaction) The burning of natural gas, wood, gasoline C 3 H 8 (g) + 5O 2 (g)  3CO 2 (g) + 4H 2 O(g)

15. Solubility and precipitation reactions Pb(NO 3 ) 2 (aq) + 2NaI (aq )  PbI 2(s) + 2NaNO 3(aq)

16. Solubility rules Soluble in water: sodium, potassium, and ammonium salts; acetates and nitrates Halides with the exception of halides of lead (II), silver(I), and mercury(I). Sulfates with the exception of sulfates of calcium, barium, lead (II) and strontium

17. Insoluble in water Phosphates, carbonates and sulfides except sodium, potassium, ammonium salts, and calcium sulfide Hydroxides except sodium, potassium, calcium, and barium hydroxides

18. Acid-Base reactions (neutralization reactions) Acid: any compound that produces hydrogen ions (H + ), when added to water. Base: any substance that produces hydroxide ions (OH - ), when added to water. HCl(aq) + Na(OH)(aq)  NaCl(aq) + H 2 O(l)