Chemical Reactions
Chapter 11.1
Describing Chemical Reactions
A. Introduction to Chemical Equations
1. What is a chemical reaction?
It is a process in which substances
are changing.
2. How do we show a chemical
reactions?
We use equation with quick,
shorthand notation to convey as
much information as possible
about what happen in a chemical
reaction.
Chemical Reactions
Chapter 11.1
Describing Chemical Reactions
A. Introduction to Chemical Equations
3. What are the two ways to
represent chemical reactions in an
equation?
Word Equation  words are used
to represent the substances.
Reactants  left side of the arrow
Products  right side of the
arrow
 yields, gives or reacts to
produce
Chemical Equation
Chapter 11.1
Describing Chemical Reactions
A. Introduction to Chemical Equations
Chemical equation  formulas of
the reactants are connected by an
arrow with the formulas of the
products
Skeleton equation  is a
chemical equation that does not
indicate the relative amounts of
the reactants and products.
Chapter 11.1
Describing Chemical Reactions
A. Introduction to Chemical Equations
4. What are the different symbols used in chemical equations?
Symbol
Explanation
+
Separates two reactants or two products

“yields”, separates reactants from products

Used in place of  for reversible reactions
(s), (l), (g)
(aq)
Heat 
Pt
Designates a reactant or product in the solid state, liquid
state and gaseous state; placed after the formula
Designates an aqueous solution; the substance is
dissolved in water; placed after the formula
Indicates that heat is supplied to the reaction
A formula written above or below the yield sign indicates
its use as a catalyst
Chapter 11.1
Describing Chemical Reactions
Remember the seven diatomic elements:
Element
Symbol
Hydrogen
H2
Nitrogen
N2
Oxygen
O2
Fluorine
F2
Chlorine
Cl2
Bromine
Br2
Iodine
I2
Chapter 11.1
Describing Chemical Reactions
A. Introduction to Chemical Equations
5. Sample Problem 11.1  Writing a Skeleton Equation
Hydrochloric acid reacts with solid sodium hydrogen carbonate. The
products formed are aqueous sodium chloride, water, and carbon
dioxide gas.
Do problems 1 and 2 on page 349 below the sample problem 11.1.
Pass out worksheet.
Chapter 11.1
Describing Chemical Reactions
B. Balancing Chemical Equations
B. Balancing Chemical Equations
1. What is a balanced equation?
b. Use coefficients to balance the
equation so that it obeys the law
of conservation of mass.
A chemical reaction in which each
side of the equation has the same
number of atoms of each element
and mass is conserved.
2. How do you write a balanced
chemical equation?
a. First write the skeleton
equation
3. What are coefficients?
Small whole numbers that are
placed in front of the formulas in
an equation in order to balance it.
Chapter 11.1
Describing Chemical Reactions
B. Balancing Chemical Equations
4. What are the rules for writing and balancing equations?
Rules for Writing and Balancing Equations
Determine the correct formulas for all the reactants and products.
Write the skeleton equation.
Determine the number of atoms of each element in the reactants and products.
Count a polyatomic ion as a single unit if it appears unchanged on both sides
Total number of particles = Coefficient x subscript
Balance the elements one at a time by using coefficients. When no coefficient is
written, it is assumed to be 1.
Never balance an equation by changing the subscripts in a chemical formula
Check each atom or polyatomic ion to be sure that the number is equal on both
sides of the equation.
Make sure all the coefficients are in the lowest possible ratio.
Chapter 11.1
Describing Chemical Reactions
5. Sample problem 11.2 Balancing a Chemical Equation.
Students suspended copper wire in a aqueous solution of silver
nitrate. They noticed a deposit of silver crystals on the copper wire
when the copper reacted with the silver nitrate.
AgNO3 (aq) + Cu(s)  Cu(NO3)2(aq) + Ag(s)
Do Problems 3 and 4 on page 352 below sample problem 11.2
Chapter 11.1
Describing Chemical Reactions
6. Sample problem 11.3 Balancing a Chemical Equation.
Aluminum is a good choice for outdoor furniture because it reacts
with oxygen in the air to form a thin protective coat of aluminum
oxide.
Al(s) + O2(g)  Al2O3(s)
Do Problems 5 and 6 on page 353 below sample problem 11.3
Pass out worksheet.
Chapter 11.2
Types of Chemical Reactions
A. Classifying Reactions
1. What are the five general types of
reactions?
a. Combination
b. Decomposition
c. Single-replacement
d. Double-replacement
e. combustion
Classifying Reactions
Chapter 11.2
Types of Chemical Reactions
A. Classifying Reactions
What is a combination reaction?
It is a chemical change in which two or
more substances react to form a single
new substance.
It is sometimes called a synthesis
reaction.
Combination Reaction
Chapter 11.2
Types of Chemical Reactions
A. Classifying Reactions
What is a decomposition reactions?
It is a chemical change in which a single
compound breaks down into two or more
simpler products.
Decomposition reaction
Chapter 11.2
Types of Chemical Reactions
A. Classifying Reactions
What is a single-replacement reaction?
It is a chemical change in which one
element replaces a second element in a
compound.
Metals replace metals.
Nonmetals replace nonmetals.
Single-replacement reaction
Chapter 11.2
Types of Chemical Reactions
A. Classifying Reactions
What is a double-replacement reaction?
It is a chemical change involving an
exchange of positive ions between two
compounds.
Double-replacement
Chapter 11.2
Types of Chemical Reactions
A. Classifying Reactions
What is a combustion reaction?
It is a chemical change in which an
element or a compound reacts with
oxygen, often producing energy in the
form of heat and light.
Combustion Reaction
Chapter 11.2
Types of Chemical Reactions
Chapter 11.3
Reactions in Aqueous Solution
A. Net Ionic Equations
Net Ionic Equations
1. What is a molecular equation?
3. What are spectator ion?
It shows all the substances in complete
formula states.
An ion that appears on both sides of an
equation and is not directly involved in
the reaction.
Pb (s) + AgNO3(aq)  Ag(s) + Pb(NO3)2(aq)
2. What is a complete ionic equation?
4. What is the net ionic equation?
It shows all the substance in ions except for
solid, liquids, or gases.
It is an equation for a reaction in solution
that shows only those particles that are
directly involved in the chemical change.
Pb(s) + Ag+(aq) + NO3-(aq)  Ag(s) +
Pb2+(aq) + NO3-(aq)
Pb(s) + Ag+(aq) Ag(s) + Pb2+(aq)
Chapter 11.3
Reactions in Aqueous Solution
Groups and charges of the families across the Periodic Table
1
2
13
14
15
16
17
18
+1
+2
+3
-4/+4
-3
-2
-1
0
Charges for other sections of the Periodic Table
Transition Metals generally have a +2
Rare Earth Elements generally have a +3
Chapter 11.3
Reactions in Aqueous Solution
A. Net Ionic Equation
B. Predicting the Formation of a Precipitate
5. Sample Problem 11.8 on page 371
1. What is a precipitate?
6. Do problems 25 and 26 on page 371.
7. Pass out worksheet
It is a formation of an insoluble salt.
(solid)
2. How can you predict the formation of a
precipitate in a double-replacement
reaction?
By using the general rules for solubility of
ionic compounds.
3. What the general rules for solubility?
Chapter 11.3
Reactions in Aqueous Solution
Compounds
Solubility
Salts of alkali metals and
ammonia
Soluble
Some lithium compounds
Nitrate Salts and
Chlorate Salts
Soluble
Few exceptions
Sulfate Salts
Soluble
Compounds of Pb, Ag, Hg,
Ba, Sr, and Ca
Chloride salts
Soluble
Compounds of Ag and some
compounds of Hg and Pb
Carbonates, Phosphates,
chromates, sulfides, and
hydroxides
Most are insoluble
Exceptions
Compounds of the alkali
metals and of ammonia
Chapter 11.3
Reactions in Aqueous Solution
4. Sample Problem 11.9 on page 373
K2CO3 (aq) + Sr(NO3)2 (aq)  KNO3 ( ) + SrCO3 ( )
5. Do the Worksheet
Time to study for the test!