Chapter 8: CHEMICAL EQUATIONS AND REACTIONS

Indications of a Rxn Heat or light given off Bubbling/smoke, gas being released Precipitate (solid) forms Change in the odor/color Chemical indicators turn color

Eqn Writing Make sure you have the correct formula for each substance Diatomic elements – exist only in pairs, always written with a 2 subscript H 2 O 2 N 2 Cl 2 Br 2 I 2 F 2

Rxn/Eqn Parts H 2 (g) + Cl 2 (g)  2 HCl (g) Reactants Product (Reagents)

Symbols Meaning Reversible rxn Heat added (formula) Catalyst:speeds up rxn (s)Solid precipitate forms (g)Gas Gas released (l)liquid (aq)Aqueous (in water)

Law of Conservation of Matter Atom values must match on both sides Balance an eqn with coefficient multipliers ___H 2 + ___O 2  ____ H 2 O 221

___Al 2 O 3  ___ Al + __O 2 __Fe(NO 3 ) 3 + __KSCN  __KNO 3 + __Fe(SCN)

5 Rxn Types

Decomposition (analysis) One Reactant breaking down into two or more products

One or more reactants combine with oxygen, O 2, must invole heat or light One or more reactants combine with oxygen, O 2, must invole heat or light Usually takes place with carbon compounds and produces carbon dioxide and water Combustion CH 4 + O 2  CO 2 + H 2 O

Single Replacement (Displacement) One element replaces a similar element in a compound

Double Replacement the interchanging of two ions from two different compounds.the interchanging of two ions from two different compounds. Products usually have a precipitate

Reaction rates The rate of disappearance of the reactants (concentration per second) Depends on activation energy and molecule collisions

Factors affecting rate: 1)Type of reactantsType of reactants ion exchange happens quick covalent bond rearrangement is slow 2) Concentration and pressure higher amount increases the collision rate.

3) Temperature – increase it and collision rate increases 4) Catalysts – increases the rate by lowering activation energy 5) Inhibitors – used to slow rate, preservatives.