Table of Contents
Chapter 10: Chemical Reactions
and Equations
10.1: Reactions and Equations
10.2: Classifying Chemical Reactions
10.3: Reactions in Aqueous Solutions
Table of Contents
Chapter 10: Chemical Reactions
and Equations
10.1: Reactions and Equations
Chemical Reactions and Equations: Basic Concepts
Writing Chemical Equations
• A substance that undergoes a reaction (a
chemical change) is called a reactant.
• Each new substance formed is called a
product.
• Reactants  Products
Chemical Reactions and Equations: Basic Concepts
Balancing Chemical Equations
• The law of conservation of mass: Matter is
neither created nor destroyed during a
chemical reaction.
• Remember that atoms don’t change in a
chemical reaction; they just rearrange.
Chemical Reactions and Equations: Basic Concepts
Balancing Chemical Equations
• Only one rule:
Atoms on the left = Atoms on the right
Chemical Reactions and Equations: Basic Concepts
Balancing Chemical Equations
• Skeleton Equations are unbalanced
chemical equations.
Not balanced!
Chemical Reactions and Equations: Basic Concepts
Balancing Chemical Equations
• Chemical Equations are balanced chemical
equations.
coefficient
Balanced!
Balancing an Equation
Basic Hints:
1. Do easiest elements first.
C5H12(g) + 8 O2(g) → 5 CO2(g) + 6 H2O(l)
2. Save element coefficient for last.
4 PH3 + 8 O2(g) → P4O10(s) + 6 H2O(g)
3. Save H & O for last, they often work themselves out.
2 Fe(OH)3 → Fe2O3 + 3 H2O
Balancing an Equation
4. Make odds even.
2 H3BO3 → B2O3(s) + 3 H2O(l)
5. Group atoms together.
3 (NH4)2CO3(aq) + 2 Al(NO3)3 (aq) →
Al2(CO3)3(s) + 6 NH4NO3(aq)
6. Always double check!
Reactants’ atoms = Products’ atoms
Try it out!
• Balancing Chemical Equations Worksheet – try 1-5
now
• The “Balancing Chemical Equations” side is due
Thursday (tomorrow)
• The “Balancing Equations Worksheet” side is for you
if you need additional practice
Chemical Reactions and Equations: Basic Concepts
Word Equations
• Reactants  Products
Chemical Equations
• Phases are indicated by the symbols (s), (l),
(g), and (aq).
Chemical Reactions and Equations: Basic Concepts
Energy and Chemical Equations
• The word energy is sometimes written in
the chemical equation.
Basic Assessment Questions
Write a word equation, a skeleton equation, and a
balanced for each of the following:
1. Solid lithium reacts with chlorine gas to produce
solid lithium chloride.
2
2
2. Nitrogen gas reacts with oxygen gas to produce
nitrogen dioxide gas.
2
2
Basic Assessment Questions
TRY IT OUT! Write a balanced chemical equation for
the following reactions.
1. Solid potassium reacts with liquid water to produce
hydrogen gas and a water solution of potassium
hydroxide.
2. Calcium chloride and sodium carbonate in water
solution produce solid calcium carbonate and a
water solution of sodium chloride.
Try it out!
• Balancing Handout
• The ODDS are due Friday
• The evens are for you if you need additional
practice
Table of Contents
Chapter 10: Chemical Reactions
and Equations
10.2: Classifying Chemical Reactions:
Chemical Reactions and Equations: Basic Concepts
Recognizing Chemical Reactions
• When a substance
undergoes a chemical
change, it takes part in
a chemical reaction.
• After it reacts, it no
longer has the same
chemical identity.
Chemical Reactions and Equations: Basic Concepts
Recognizing Chemical Reactions
• Many important clues indicate when chemical
reactions occur.
• Change in temperature
• Change in color
• Change in odor
• Change in appearance such as phase
Chemical Reactions and Equations: Basic Concepts
Major Classes of Reactions
• If you can classify a reaction into one of
five major categories by recognizing
patterns that occur, you already know a
lot about the reaction.
Click box to view
movie clip.
Chemical Reactions and Equations: Basic Concepts
A Synthesis Reaction
A + B → AB
Chemical Reactions and Equations: Basic Concepts
A Decomposition Reaction
MCO3(s) → MO(s) + CO2(g)
MOH(s) → MO(s) + H2O(g)
MHCO3(s) → MO(s) + H2O + CO2(g)
AB → A + B
Chemical Reactions and Equations: Basic Concepts
Single Displacement
A + BC → B + AC
Activity Series
For this type of reaction to occur, the “replacing”
element MUST be more reactive than the “replaced”
element. See table of reduction potentials.
P. 288
METALS
Lithium
Rubidium
Potassium
Calcium
Sodium
Magnesium
Aluminum
Manganese
Zinc
Iron
Nickel
Tin
Lead
Copper
Silver
Platinum
Gold
Most active
P. 288
HALOGENS
Fluorine
Chlorine
Bromine
Iodine
Least active
Activity Series
F2(g) + 2NaBr(aq) → 2NaF(aq) + Br2(l)
More active than Br
Br2(g) + 2NaF(aq) → NR
Less active than F
Most
active HALOGENS
Fluorine
Chlorine
Bromine
Iodine
Least active
Chemical Reactions and Equations: Basic Concepts
Double Displacement
AB + CD → AD + CB
Chemical Reactions and Equations: Basic Concepts
Combustion
CxHyOz + O2 → CO2 + H2O
Basic Assessment Questions
Identify each of the following skeleton equations.
Balance each equation if necessary.
synthesis
decomposition
• You should be able to…
o Identify types of reactions
o Predict products
• Look at reactants
• What can they form? What is most likely?
• We will get more practice tomorrow and
Monday
Table of Contents
Chapter 10: Chemical Reactions
and Equations
10.3: Reactions in Aqueous Solutions:
Chemical Reactions and Equations: Additional Concepts
REVIEW
• With those at your table, please name and
define the 5 classifications of reactions
Chemical Reactions and Equations: Additional Concepts
REVIEW
• An iron bar reacts with oxygen to form rust.
• What kind of reaction will take place?
• What will the products be?
H2O
4Fe(s) + 3O2(g) → 2Fe2O3(s)
synthesis
Chemical Reactions and Equations: Additional Concepts
REVIEW
• A copper wire is dipped into a silver nitrate
solution.
• What kind of reaction will take place?
• What will the products be?
Cu(s) + AgNO3(aq) → Ag(s) + CuNO3(aq)
Single displacement
Chemical Reactions and Equations: Additional Concepts
REVIEW
• Methane gas (CH4) from a Bunsen burner is
lit on fire.
• What kind of reaction will take place?
• What will the products be?
CH4(g) + O2(g) → CO2(g) + H2O(g)
Combustion
Chemical Reactions and Equations: Additional Concepts
REVIEW
• A Hydrogen balloon is lit on fire.
• What kind of reaction will take place?
• What will the products be?
2H(g) + O2(g) → 2H2O(g)
synthesis / combustion
Chemical Reactions and Equations: Additional Concepts
Reactions in Aqueous Solutions
• Solutions of calcium chloride and
ammonium sulfate are mixed to form solid
calcium sulfate.
• What kind of reaction will take place?
• What will the products be?
CaCl2(aq) + (NH4)2SO4(aq) → CaSO4(s) + 2NH4Cl(aq)
Double displacement
Chemical Reactions and Equations: Basic Concepts
Double Displacement
For aqueous solutions to react in a double
displacement reactions, one of the
products MUST come out of solution:
1. solid (precipitate) – see solubility rules
2. H2O or
3. gas – bubbles/odor
Chemical Reactions and Equations: Additional Concepts
Reactions in Aqueous Solutions
precipitate
• Check solubility on the back of the periodic
table to see if a precipitate forms
• If insoluble – it’s a precipitate
Chemical Reactions and Equations: Additional Concepts
Reactions in Aqueous Solutions
• To show all of the particles in solution as
they really exist, a complete ionic equation
can be written.
• The sodium and nitrate ions are on both sides
of the equation.
• Such ions that do not participate in a reaction
are called spectator ions.
Chemical Reactions and Equations: Additional Concepts
Reactions in Aqueous Solutions
• An ionic equation that does not show spectator ions
but only the particles that participate in a reaction is
called a net ionic equation.
• In net ionic equations, (s), (l), (g) are never
cancelled out.
Chemical Reactions and Equations: Additional Concepts
Writing Ionic Equations
• Write the balanced chemical equation for the
reaction between aqueous solutions of
strontium nitrate and potassium sulfate, which
forms the precipitate strontium sulfate.
• Then write the complete ionic and net ionic
equations.
Chemical Reactions and Equations: Additional Concepts
Writing Ionic Equations
• strontium nitrate (aq) + potassium sulfate (aq) →
strontium sulfate (s) + ?
1. Write the correct skeleton equation.
2. Use coefficients to produce the balanced chemical
equation.
Chemical Reactions and Equations: Additional Concepts
Writing Ionic Equations
3. Write the complete/total ionic equation.
How to know when to split a compound:
• Split only ionic (aq) compounds & strong
acids (HCl, H2SO4, HNO3)
• Leave molecules and weak acids alone!
(HF, HCH3COO)
Chemical Reactions and Equations: Additional Concepts
Writing Ionic Equations
4. Cross out the spectator ions, which are those
that are on both sides of the equation.
5. That leaves the net ionic equation.
Chemical Reactions and Equations: Additional Concepts
Writing Ionic Equations
• Define:
• Word equation
equation written in words
• Skeleton equation unbalanced, symbols
• Balanced equation balanced, symbols
• Complete/total ionic equation broken into ions
• Net ionic equation
spectators removed
Try it out!
• Chemical Equations worksheet
o (we will have time to work on it on Monday)
• Due Tuesday, 13 March
• Due TODAY at the end of class: Balancing Handout
Chemical Reactions and Equations: Additional Concepts
Reactions that form water or a gas
• When hydrochloric acid and potassium hydroxide
solutions are mixed, water results, together with an
aqueous solution of potassium chloride.
• Write the balanced chemical equation, a complete
ionic equation, and a net ionic equation for this
reaction.
• The balanced chemical equation is the same
as the skeleton equation.
Chemical Reactions and Equations: Additional Concepts
Reactions that form water or a gas
• Write the complete ionic equation, which
includes all of the ions.
• Remove the spectator ions to produce the net
ionic equation.
Additional Assessment Questions
Question 1
Write a balanced chemical, complete ionic, and
net ionic equations for the following reaction:
Aqueous solutions of lead(II) nitrate and
ammonium chloride are mixed, forming a
precipitate.
Additional Assessment Questions
Answer
Chemical:
Complete Ionic:
Net ionic:
Additional Assessment Questions
Question 2
Write a balanced chemical, complete ionic,
and net ionic equations for the reaction
between the following substances, which
produce water:
nitric acid (HNO3) and aqueous barium
hydroxide.
Additional Assessment Questions
Answer
Chemical:
Complete ionic:
Net ionic:
or, with coefficients reduced to lowest terms,
Additional Assessment Questions
Question 3
Write a balanced chemical, complete ionic,
and net ionic equations for the reaction
between the following substances, which
produce a gas:
hydrochloric acid and aqueous sodium
cyanide, with production of a gas.
Additional Assessment Questions
Answer
Chemical:
Complete ionic:
Net ionic:
QUIZ
• Tell the classification of the following particles either
ionic, molecular, strong acid, weak acid, or
element.
• Tell if each of the following particles are soluble or
insoluble. If soluble, then put the phase as (aq) and
show how the particle dissolves (splits). If insoluble,
put the appropriate phase (s), (l), (g).