Chapter 8 (cont.) TYPES OF REACTIONS- patterns observed empirically allow prediction of products when reactants are known

SYNTHESIS  More complex product made from simpler substances  General format : A + X → AX element + element → compound  EX: Sodium + chlorine → Magnesium + nitrogen → Sodium + oxygen →

DECOMPOSITION  A single reactant is broken down into simpler substances  AX → A + X CMPD → ELEMENT + ELEMENT Most require an input of energy to break the bonds in the reactants.  EX: water →  magnesium bromide →

SINGLE REPLACEMENT REACTIONS  An element on its own pushes another SIMILAR element out of a cmpd (replaces it)  An element can only be replaced by a more active element. Check activity series to decide if rxn will occur.  A + BX → AX + B element + cmpd → different cmpd + diff. elem. Ex: Al (s) + CuCl 2 → OR: Y + BX → BY + X Ex: Cl 2 + NaBr →

Examples:  iron is added to a solution of silver nitrate (assume Fe 3+ )  A piece of sodium is dropped into water  Fluorine is bubbled into a solution of potassium iodide

Single Replacement (cont.)  More active metals get oxidized (give up electrons more easily to form positive ions), less active metals will accept them-get reduced LEO GER Atoms of uncombined elements have 0 oxidation number.  More active nonmetals gain electrons (get reduced) more easily & form negative ions  Reactions where e - ’s are transferred can be classified as oxidation-reduction or redox reactions.

DOUBLE REPLACEMENT REACTIONS  “IONS SWITCH PARTNERS”  AX + BY → AY + BX Cmpd + cmpd → two different compounds 1.Precipitation Rxns a)One product is soluble, the other is not b)Use solubility rules to determine if there is a precipitate EX: NaCl (aq) + AgCH 3 COO (aq) →

1. Precipitation Rxns (cont)  Ex: Solutions of barium nitrate and sodium sulfate are combined:  Solutions of lithium sulfate and magnesium bromide are combined.

2. Acid/Base Neutralization  Acid + base → salt + water (H + )(OH - ) nitric acid + lithium hydroxide → sulfuric acid + potassium hydroxide → Acetic acid + barium hydroxide →

Net Ionic Equations 1.Formula Unit Equation- normal balanced equation including states (NH 4 ) 2 S (aq) + Cd(NO 3 ) 2 (aq) → 2. Total Ionic Equation – all aqueous substances are separated into ions. Note: polyatomic ions stay together as a group. Cancel all spectator ions 3. Net ionic equation- rewrite remaining equation w/states

Combustion Reactions  Hydrocarbon + oxygen → carbon dioxide + water C x H y + O 2 → CO 2 + H 2 O Ex: Liquid decane, C 10 H 22, is burnt in air

 Ammonium dichromate (Cr 2 O 7 2- ) decomposes with heating into chromium (III) oxide, nitrogen, and water vapor.  White phosphorus (P 4 ) ignites spontaneously in air to form solid tetraphosphorus decaoxide.

 Ammonium nitrate is used as a fertilizer even though it can be explosive. It can be made by bubbling ammonia gas (NH 3 ) through a solution of nitric acid.  An electric current is passed through a sodium chloride solution and forms sodium hydroxide, chlorine and hydrogen. The water in the solution participates in the reaction.