
Chemical reactions can be classified in one
of two ways:
1. Based on how atoms are reordered
2. Based on how energy/ heat is transferred
Two or more elements/compounds combine to
form a single product.
General equation: A + B  AB
2Mg + O2  2MgO
A
B
AB
 2Mg + O2  2MgO(white powder)
 A + B  AB
8 Fe + S8  8 FeS
+

A single reactant/compound, breaks into
two or more parts.
General equation: ABA + B
o
AB
2H2O2  2H2O + O2
A
B
 2H2O2 2H2O +O2
 AB  A + B
 Bubbles are O2
 Liquid is water.
 Elephant’s
toothpaste
MgO2  Mg

+ O2
+

+
A
BC
AC
B
A more reactive Single element replaces a less
reactive element in a compound. (metal replaces
another metal… a non-metal replaces a nonmetal)
The general equation:
(Rico Suave Scandal)
A + BC  AC + B
 Al + CuCl2  AlCl3 + Cu
 A + BC  BA + C
 Mg + 2HCl  MgCl2 + H2
 A + BC  BA + C
 What do you know about
Hydrogen gas!?
2Mg +2HCl 2 MgCl
_____ + H
_____
2
If a metal will only replace a metal, and a
non-metal will only replace a non-metal…
then what will the products be??
Mg kicks out H so that Mg can bond with
Cl.
BUT WAIT!!! H is the leader of the NOF 7
group – so it’s diatomic!
BUT WAIT!!! Is it balanced??
MgCl2 + __________
Al
Mg + AlCl3  ________
NaCl + __________
Br2
Cl2 + NaBr  ________
Copper(II) + silver nitrate yields …
Ag(NO3)  Cu(NO3)2
Ag
Cu _______
_____+
_________ + _______

Single Replacement
+


+
Single Replacement

+
+
CD
AB
CB
AD
Two compounds switch partners to form two
new compounds
General equation: AB + CD  AD + CB
KI+ Pb(NO3)2  KNO3 + PbI
Note: “Metals” replace “metals” and non-metals
replace non-metals
Scandal of Scandals!!


KI(aq) + Pb(NO3)2(aq)  KNO3(aq) + PbI(s)
AB + CD
 AD + CB
CaCl2+ ________
MgCl2+ Ca(SO4)  _____
MgSO4
If a metal will only replace a metal, and a nonmetal will only replace a non-metal… then
what will the products be??
Mg kicks out Ca so that Mg can bond with SO4.
 BUT WAIT!!! Make sure CaCl has the right
formula. (Ca2+ … Cl 1-)
 BUT WAIT!!! Is it balanced??
+


+
Double Replacement

Double Replacement
Pb (NO3)2 + K I
Pb(NO3)2 + K I  KNO3 + PbI2
+

+
C H
A hydrocarbon or alcohol is reacted with
oxygen gas to always form the products carbon
dioxide and water.
General equation:
Hydrocarbon + O2  CO2+ H2O
or Alcohol
 CH4 + O2  CO2 + H2O

C10H8 + 12 O2 ---> 10 CO2 + 4 H2O

Combustion
Hint: Look for CO2
and H2O as products!!
Unfortunately we cannot forget about neutralization reactions (a.k.a. acidbase reactions)! 
Acid and a base react to form a salt and
water.
General equation: HX + MOH  MX +H2O
HCl + NaOH  NaCl + H2O
Where M is a metal and X is a non-metal
 HBr + NaOH ---> NaBr + H2O

Neutralization
1.
EXOTHERMIC (exo= outside)- energy is released
as a product during a chemical reaction given off
as heat (hot rxn!!)
H2O2  O2 + H2O + Heat (heat is a product)
1.
ENDOTHERMIC (endo= inside)- energy is required
(a reactant) during a chemical reaction and heat is
absorbed (cold rxn!!)
2NH4 + H2O + Heat  2NH4(OH) (heat is a reactant)
Brrr…
Sodium acetate
in water