There are several types of chemical reactions: 1) Combination reactions involve two or more substances combining to form a new compound such as reactions of elements with oxygen or metals with halogens. 2) Decomposition reactions involve a single compound breaking down into simpler substances like the decomposition of water into hydrogen and oxygen gases. 3) Single replacement reactions involve a reaction where one element replaces another in a compound such as a metal replacing hydrogen in an acid. 4) Double replacement reactions involve the ions of two compounds exchanging places to form two new compounds, often with a precipitate forming.

1. Reaction Types

2. Combination (Synthesis) Reactions
Two or more substances combine to
form a new compound.
A + X  AX
 Reaction of elements with oxygen
and sulfur
 Reactions of metals with Halogens
 Synthesis Reactions with Oxides
 There are others not covered here!

3. Decomposition Reactions
A single compound undergoes a reaction
that produces two or more simpler
substances
AX  A + X
Decomposition of:
Binary compounds H2O(l )  2H2(g) + O2(g)
Metal carbonates CaCO3(s)  CaO(s) + CO2(g)
Metal hydroxides Ca(OH)2(s)  CaO(s) + H2O(g)
Metal chlorates 2KClO3(s)  2KCl(s) + 3O2(g)
Oxyacids H2CO3(aq)  CO2(g) + H2O(l )

4. Single Replacement Reactions
A + BX  AX + B
BX + Y  BY + X
Replacement of:
 Metals by another metal
 Hydrogen in water by a metal
 Hydrogen in an acid by a metal
 Halogens by more active halogens

5. Lithium
Potassium The Activity Series
Calcium of the Metals
Sodium
Magnesium
Aluminum  Metals can replace other
Zinc metals provided that they
Chromium are above the metal that
Iron
they are trying to replace
Nickel
Lead
Hydrogen  Metals above hydrogen can
Bismuth replace hydrogen in acids.
Copper
Mercury
Silver  Metals from sodium upward
Platinum can replace hydrogen in water
Gold

6. The Activity Series of the Halogens
Fluorine Halogens can replace
Chlorine other halogens in
Bromine compounds, provided
Iodine that they are above the
halogen that they are
trying to replace.
2NaCl(s) + F2(g)  ???
2NaF(s) + Cl2(g)
MgCl2(s) + Br2(g)  ??? Reaction
No

7. Double Replacement Reactions
The ions of two compounds exchange
places in an aqueous solution to form
two new compounds.
AX + BY  AY + BX
One of the compounds formed is
usually a precipitate, an insoluble gas
that bubbles out of solution, or a
molecular compound, usually water.

8. Combustion Reactions
A substance combines with oxygen,
releasing a large amount of energy in
the form of light and heat.
Reactive elements combine with oxygen
P4(s) + 5O2(g)  P4O10(s)
(This is also a synthesis reaction)
The burning of natural gas, wood,
gasoline
C3H8(g) + 5O2(g)  3CO2(g) + 4H2O(g)