Classifying Chemical Reactions Section 8.3

5 Main Reaction Types  Combustion  Synthesis  Polymerization  Decomposition  Single Displacement  Double Displacement

Combustion  Combustion = the oxidation reaction of an organic cmpd, in which heat is released  General form: Fuel + O 2  H 2 O + CO 2 + E  Fuel is a hydrocarbon, C n H n

Synthesis  Synthesis – a rxn in which 2 or more substances combine to form a new cmpd  General form: A + B  AB  2 small  1 large  Ca + Cl 2  CaCl 2

Decomposition  Decomposition – a rxn in which a single cmpd breaks down to form two or more simpler substances  General form: AB  A + B  2H 2 O (l)  2H 2 (g) + O 2 (g)

Single Displacement  Displacement reaction – chemical rxn in which one element replaces another element in a compound that is in solution  General form of s.d. = A + BC  AC + B

Single Displacement  2Al (s) +3CuCl 2(aq)  2AlCl 3(aq) +3Cu (s)  1 element displaces another – use activity series to determine if one will displace the other  Activity Series – a series of elements that have similar properties & that arranged in descending order of chemical activity

Using the Activity Series  The more readily an element reacts w/other substances, the greater its activity.  An element from above can displace another below it but not vice versa  The farther apart, the more likely the top will displace the bottom.

Double Displacement  Double displacement reaction – a rxn in which a gas, a solid ppt, or molecular cmpd forms from the apparent exchange of atoms or ions b/t 2 cmpds  General form: AB + CD  AD + CB

Double Displacement  2KI (aq) +Pb(NO) 2(aq)  PbI 2(s) + 2KNO 3(aq)  2KI (aq) +Pb(NO 3 ) 2(aq)  PbI 2(s) + 2KNO 3(aq)  K and Pb have switched places  Cations will displace cations only

Double Displacement  More accurately written as net ionic equations  Net ionic equation – equation that includes only those cmpds. and ions that are involved in a chemical change in a rxn.

Double Displacement  2K + (aq) + 2I - (aq) + Pb 2+ (aq) + 2NO 3 - (aq)  PbI 2(s) + 2K + (aq) + 2NO 3 - (aq)  NIE= Pb 2+ (aq) + 2I - (aq)  PbI 2(s)  Ions that were removed are:  Spectator ions – ions that remained unchanged in a chemical rxn.