Mullis1 Patterns of Chemical Reactivity Periodic Table predicts the chemical properties of compounds of elements. Ex: All alkali metals react with water: 2Na(s) + 2H 2 O(l) 2NaOH(aq) + H 2 (g) –These reactions become more vigorous moving from Li to Cs. –Sodium reacts with water to produce an orange flame. –Potassium and water produces a blue flame and enough heat that the hydrogen gas produced ignites with a loud pop.

Mullis2 Combustion in Air Combustion reactions are rapid reactions that produce a flame. Combustion is the burning of a substance in air. Ex: Propane combusts to produce carbon dioxide and water. C 3 H 8 (g) + 5O 2 (g)3CO 2 (g) + 4H 2 O(l)

Mullis3 Combination (Synthesis) Two or more substances react to form one product. Combination reactions have more reactants than products. Ex: 2Mg(s) + O 2 (g)2MgO(s) –Mg = closely packed atoms –O 2 = dispersed molecules –MgO = lattice of Mg 2+ and O 2- ions (ionic compound)

4 Specific Synthesis (Combination) Reactions A + B → AB Memorize these! 1.Metal oxide and water produce a base (OH - ): a)X 2 O + H 2 O → 2XOH for metals with +1 charge b)XO + H 2 O → X(OH) 2 for metals with +2 charge 2.Non-metal oxide and water produce acid (H + ): a)SO 2 + H 2 O →H 2 SO 3 b)CO 2 + H 2 O →H 2 CO 3

Mullis5 Synthesis, A + B → AB 3.Metal oxides and CO 2 produce carbonates: a)CaO + CO 2 → CaCO 3 b)Li 2 O + CO 2 → Li 2 CO 3 4.Metal oxides and water produce hydroxides: a)MgO + H 2 O → Mg(OH) 2 b)Na 2 O + H 2 O → 2NaOH 5. Special reactions: PCl 3 + Cl 2 → PCl 5 NH 3 + BF 3 → H 3 NBF 3

Mullis6 Decomposition One substance undergoes a reaction to produce two or more other substances. Decomposition reactions have more products than reactants. Ex: Consider the reaction in a car’s airbag: 2NaN 3 (s) 2Na(s) + 3N 2 (g) –Sodium azide decomposes into sodium and nitrogen.

Mullis7 Specific Decomposition Reactions AB A + B 1.Binary compounds split up a.Electrolysis is decomposition by electric current Example: H 2 O2H 2 + O 2 b.Electrolysis is decomposition by electric current 2.Metals with carbonates a.Metal oxide and carbon dioxide are formed b.Example: CaCO 3 CaO + CO 2 3.Metal hydroxides a.When heated, metal hydroxides decompose to metal oxide and water. b.Example: Ca(OH) 2 CaO + H 2 O electricity

Mullis8 Decomposition Reactions, cont. 4.Metal chlorates a.When heated, metal chlorates decompose to metal chloride and oxygen. b.Example: 2KClO 3 2KCl + 3O 2 5.Carbonic acid H 2 CO 3 →CO 2 + H 2 O 6. Sulfurous acid H 2 SO 3 →SO 2 + H 2 O

Mullis9 Decomposition Reactions, cont. 7. Ammonia(g) production NH 4 OH→NH 3 + H 2 O 8. Ammonium carbonate (NH 4 ) 2 CO 3 →2NH 3 + H 2 O + CO 2 9. Hydrogen peroxide 2H 2 O 2 →2H 2 O + 3O 2

Mullis10 Single Replacement Reactions C + AB A + CB 1.Metal replaces another metal Replacing metal must be the more active metal! Example: 2Al + 3Pb(NO 3 ) 2 3Pb + 2Al(NO 3 ) 3 2.Metal replaces H in water a.Active metals produce metal hydroxide and water b.Less reactive metals make metal oxide and hydrogen gas Examples: 2Na + 2H 2 O2NaOH + H 2 3Fe + 4H 2 OFe 3 O 4 + 4H 2

Mullis11 Single Replacement Reactions, cont. C + AB →A + CB 3.Metal replaces H in an acid Example: Mg + 2HCl→ H 2 + MgCl 2 4.Halogen replaces another halogen Fluorine is most reactive and replaces others. Example: Cl 2 + 2KBr→2KCl + Br 2 Br 2 + 2KCl→No reaction

Mullis12 Double Replacement Reactions AB + CD AD + CB 1.Precipitate forms (a salt). Example: 2KI(aq) + Pb(NO 3 ) 2 (aq)PbI 2 (s) + 2KNO 3 (aq) 2.Gas forms. FeS(s) + 2HCl(aq)H 2 S (g) + 2FeCl 2 (aq) 3.Water forms. NaOH(aq) + HCl(aq)NaCl (aq) + H 2 O (l)