Types of Chemical Reactions –Part I Mrs. Coyle Chemistry

Types of Chemical Reactions Composition Decomposition Single Replacement (Displacement) Double Replacement (Displacement) Combustion Oxidation-Reduction

Composition (Combination, Synthesis) Two or more substances combine to form a single substance. General equation: A + B  AB example: 2Na + Cl 2  2NaCl 0/Movies/NACL1.html

Decomposition A compound is broken into two or more products. General equation: AB  A + B example: 2H 2 O  2H 2 + O 2

Single Replacement A + BC  AC +B

Activity Series For an element to replace another the lone element must be more active than the element it is replacing in the substance. See the reference chart behind your periodic table.

Example: Zn+ 2 HCl  ZnCl 2 + H 2

Example: Thermite Reaction 2 Al + Fe 2 O 3  Al 2 O Fe

Example: 2NaBr (aq) + Cl 2 (g)  2NaCl (aq) + Br 2 (g)

Examples: Ca + Al(NO 3 ) 3  K + Na 2 SO 4 

Double Replacement (Double Displacement) AB + CD  AD + CB

Double Replacement Reactions Occur in aqueous solutions For a DR reaction to occur one of the following must happen: 1. A precipitate is formed (an insoluble or slightly soluble solid). 2. A molecular compound (usually water is formed). 3. A gas is formed.

Example: Production of a Precipitate Silver Nitrate + Sodium Chloride Precipitate AgCl (s)

Solubility Rules See the reference chart behind your periodic table.

Example: Production of H 2 O H 2 SO 4 (aq)+2NaOH(aq)  2H 2 O(l) +Na 2 SO 4 (aq)

3 Ways to Write Equations Involving Reactions in Solutions 1. Formula Equation ex: Zn(s) +2HCl(aq)  ZnCl 2 (aq) + H 2 (g) 2. Complete Ionic Equation Zn(s) +2H + (aq)+2Cl - (aq)  Zn +2 (aq)+ 2Cl - (aq) + H 2 (g) 2. Net Ionic Equation Zn(s) +2H + (aq)  Zn +2 (aq)+H 2 (g)

Note: Spectator ions are ions that do not undergo chemical change during the reaction. In a net ionic equation the charge and the atoms must balance.