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 + Belement + cmpd → different cmpd + diff. elem.

Ex: Al (s) + CuCl2 → OR: Y + BX → BY + X

Ex: Cl2 + NaBr →

Examples:

iron is added to a solution of silver nitrate (assume Fe3+)

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) + AgCH3COO (aq) →

1. Precipitation Rxns (cont)

Ex: Solutions of barium nitrateand 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

(NH4)2S(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

CxHy + O2 → CO2 + H2O

Ex: Liquid decane, C10H22 , is burnt in air

Ammonium dichromate (Cr2O72-)

decomposes with heating into chromium (III) oxide, nitrogen, and water vapor.

White phosphorus (P4) 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 (NH3) 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.