Prep Materials for College-Level Chemistry
CHEMICAL REACTIONS
Chemical reactions involve chemical changes—those changes in which bonds are broken and new bonds
are formed such that one or more new substances are made. To memorize all possible chemical reactions
would be daunting at best—there are so many. Instead, we prefer to classify reactions by type. A table
summarizing reaction types is provided below.
Reaction Types with Examples
Recognizing chemical changes by reaction type is valuable for being able to predict products and to
predict reactivity/stability. It is also an important concept for stoichiometry, acid/base, equilibrium, and
many more relevant-to-living questions.
(NOTE: Reactions may be of more than one type!)
Combustion
Complete combustion:
C + O2 CO2
Fuel + O2 CO2 + H2O
Incomplete combustion:
Fuel + O2 CO + H2O
Combination
Two or more substances combine into
a single product.
H2O + SO3 H2SO4
Dissociation
Ionic compound separates into
component ions (often, in water).
KCl K
Displacement
Single element replaces another
element, forming a new compound.
Required: single element must be
more reactive than that it replaces.
Fe(s) + 2HCl(aq) FeCl2(aq) + H2(g)
Decomposition
Single compound breaks into
component elements.
2HgO(s) 2Hg(l) + O2(g)
Metathesis
aka Double-displacement
AgNO3(aq) + NaCl(aq) “Trade partners”
+
-
(aq)
+ Cl (aq)
AgCl(s) + NaNO3(aq)
Neutralization
Acid + Base Salt + Water
HCl + NaOH HOH + NaCl(all aqueous)
Precipitation
Any reaction that produces a solid
product.
AlCl3(aq) + 3NaOH(aq) Al(OH)3(s) + 3NaCl(aq)
Reduction –
Oxidation (REDOX)
Any reaction that involves a change in
oxidation state for its atoms.
Fe2O3 + 3CO 2Fe + 3CO2