Chem 121
Summary of Types of Chemical Reactions
Page 1
Rxns 1, 2A & 2B are “double replacement or metathesis” reactions: AB + CD  AD + CB
(Think about why it’s CB and BC.)
1. Precipitation Type –Reaction between two ionic compounds.
If one or more of the product is insoluble in water, it is called a precipitate, and we say that
“reaction goes.” CHECK SOLUBILITY RULES.
e.g.
2NaCl (aq) + Pb(NO3)2 (aq)  2NaNO3 (aq) + PbCl2 (s)
2. Acid-Base Reaction Type – Reaction between an acid and a base falls roughly in 3 categories, all
involve the transfer of H+ to the other reactant:
Note 1: An acid is easily recognized by the H in front of the formula. A base may or may not contain the
hydroxide (OH–) ion necessarily. In more advanced courses, H may be elsewhere.
Note 2: In this class, all acid-base reactions will go. You will be taught exceptions in higher level courses.
Note 3: Despite what you may have learned previously, not all acid-base reactions will produce “salt and
water.” Some will produce a salt only, without producing water.
A) Reaction of an acid with a hydroxide base: (a double replacement reaction)
H+ and the cation exchange places, and water is formed.
e.g.
H2SO4 (aq) + 2NaOH (aq)  Na2SO4 (aq) + 2H2O (l)
B) Reaction of an acid with a carbonate, sulfite or sulfide compound containing typically
CO32–, HCO3–, SO32– HSO3–, S2– or HS–. (a double replacement reaction)
e.g. 2HCl (aq) + Na2CO3 (aq)  H2CO3 (aq)
+ 2NaCl (aq)
 H2O (l) + CO2 (g) + 2NaCl (aq)
These are known as “gas producing reactions.” Driving force is the release of the gas.
C) Reaction of an acid with a N-base, without OH– (not a double replacement reaction)
H+ is transferred from the acid to the base and a salt is formed. Water is not formed.
e.g.
HCl (aq) + NH3 (aq)  NH4Cl (aq)
3. Oxidation-Reduction Reaction (redox)  Reaction involves transfer of electrons from one reactant
to another, thus changing the oxidation state of one or more of the reactants. You should be able to
recognize any redox reaction by noting a change in oxidation numbers, and be able to predict products
for only combustion and single replacement types of redox reactions:
A) Single Replacement type of redox reactions: A + BC  AC + B
e.g.
Cu (s) + 2HBr (aq)  CuBr2 (aq) + H2 (g)
Change in oxidation numbers: Cu has changed from Cu° to Cu2+ and H+ has changed to H2.
Single replacement: Cu has replaced H to form CuBr 2.
Note 1: Reaction will go only if the single element is active enough to do the replacement.
CHECK THE ACTIVITY SERIES.
Note 2: There are many redox reactions that are NOT single replacement.
B) Combustion – Exothermic reaction with O2 (redox)
Note: Products are oxides of each element in the reactant.
e.g.
CH4 (g) + O2 (g)  CO2 (g) + 2H2O (g) + heat
C) Other redox reactions: e.g. NaI + 3HOCl  NaIO3 + 3HCl (You do not need to predict
products must recognize it is a redox reaction because of changes in oxidation numbers)
Combination – Reaction of 2 reactants combining to form one product
e.g.
C6H12 (l) + Br2 (l)  C6H12Br2 (l)
Note: Combustion is a type of combination reaction.
Decomposition – Reactant breaking into two or more substances
e.g.
2KClO3 (s) 2KCl (s) + 3O2 (g)
4. Metal oxides react with water to form metal hydroxides e.g. Na2O (s) + H2O (l)  2NaOH (aq)
Nonmetal oxides react with water form acids e.g. SO3 (l) + H2O (l)  H2SO4 (aq)
Note: Reactions of metals with water come under Type 3A above.
CHEM 121
Examples of Chemical Reactions
This is not homework to be handed in but a highly recommended exercise. We will go over some of it in
class. The rest is just practice for you. Get help at my office or with a tutor if necessary.
I. Identify which type of reactions are involved:
A. Precipitation Type
B. Acid-Base
C. Gas producing
D. Redox
E. Rxn of oxides with water
F. Other (none of the above)
II. Give the formula & physical states of the products WITHOUT BALANCING THE EQUATION.
III. Balance the equation.
IV. Write above the arrow: Yes for reactions that you predict will go.
NR for reactions that you predict “No Reaction.”
1. Sr(NO3)2 (aq) + H2SO4 (aq) 
TYPE OF REACTION: A B C D E
F
2. K2O (s) + H2O (l) 
TYPE OF REACTION: A B C D E
F
3. Fe(NO3)2 + KOH (aq) 
TYPE OF REACTION: A B C D E
F
4. Mn2(CO3)3 (s) + 2HBr (aq) 
TYPE OF REACTION: A B C D E
F
5. SO3 (g) + H2O (l) 
TYPE OF REACTION: A B C D E
F
Ignore “2”.
6. C18H36O (l) + O2 (g) 
TYPE OF REACTION: A B C D E
F
7. HNO3 (aq) + Co(HCO3)3
TYPE OF REACTION: A B C D E
F
8. Ni (s) + HNO3 (aq) 
TYPE OF REACTION: A B C D E
F
9. Ba (s) + H2O (l) 
TYPE OF REACTION: A B C D E
F
Hint: coeff.of bal.eqn=2, 23, 16, 16 (ignore)
10. Ba(OH)2 (aq) + excess HNO3 (aq) 
TYPE OF REACTION: A B C D E F