Chemistry Chapter 8
Chemical Equations
Balancing Formula Equations
What is a Chemical Reaction?
• A chemical reaction occurs when two or
more substances are changed into
different substances.
What is a Chemical Equation?
A chemical equation represents, with
symbols and formulas, the identities and
relative molecular or molar amounts of the
reactants and products in a chemical
reaction.
Indications of a Chemical
Reaction
1) Evolution of energy
as heat and light.
2) Production of a
gas.
3) Formation of a
precipitate.
4) Color change.
Characteristics of Chemical Equations
1) The equation must represent known facts.
2) The equation MUST contain the correct
formulas for the reactants and products.
3) The Law of Conservation of Mass must be
satisfied. We can use coefficients to satisfy
this law.
*coefficients- a small whole
number that appears in front of a
formula in a chemical equation
Word & Formula Equations
• word equation- an equation in which the
reactants and products of a reaction are
represented by words
• formula equation- represents the reactants
and products of a chemical reaction by their
symbols & formulas
• balanced formula equation- uses coefficients
to allow conservation of mass
Examples of the Types of Equations
word equationiron II phosphate reacts with aluminum nitrate to
produce iron II nitrate and aluminum phosphate
formula equationFe3(PO4)2 + Al(NO3)3  Fe(NO3)2 + AlPO4
balanced formula equationFe3(PO4)2 + 2 Al(NO3)3  3 Fe(NO3)2 + 2 AlPO4
Symbols Used in Chemical
Equations

yields
(s)
solid
(l)
liquid
(aq)
aqueous
(g)
gas
Diatomic Elements
• There are seven common elements that are called
the “diatomic elements”. Whenever they are pure
elements and appear alone (NOT in a compound) in
an equation, their symbol contains two atoms rather
than one. They include:
hydrogen (H2)
fluorine (F2)
iodine (I2)
oxygen (O2)
chlorine (Cl2)
nitrogen (N2)
bromine (Br2)
A simple mnemonic is “halogens HON”.
Practice Problems
• Do practice
problems #1, #2,
& #3 on page 268
of the textbook.
Practice Problem 1 page 268
1a) Ca (s) + S (s)  CaS (s) already balanced
1b) H2 (g) + F2 (g)  HF (g)
H2 (g) + F2 (g)  2 HF (g)
1c)
balanced
Al (S) + ZnCl2 (aq)  Zn (s) + AlCl3 (aq)
2 Al(S) + 3 ZnCl2 (aq)  3 Zn(s) + 2 AlCl3(aq)
Practice Problem #2 page 268
2a) CS2(l) + O2(g)  CO2(g) + SO2(g)
liquid carbon disulfide reacts with oxygen
gas to produce carbon dioxide gas and
sulfur dioxide gas
2b) NaCl(aq) + AgNO3(aq)  NaNO3(aq) + AgCl(s)
aqueous sodium chloride reacts with
aqueous silver nitrate to yield aqueous
sodium nitrate and solid silver chloride
Practice problem #3 page 268
3) N2H4 + O2  N2 (g) + H2O
N2H4 + O2  N2 (g) + 2 H2O
Significance of a Chemical Equation
1) The coefficients of a chemical reaction
indicate relative, not absolute, amounts of
reactants and products.
2) The relative masses of the reactants and
products of a chemical reaction can be
determined from the reaction’s coefficients.
3) The reverse reaction for a chemical equation
has the same relative amounts of substances
as the forward reaction.
Rules for Balancing Chemical Equations
1) Identify the names of the reactants and products and
write a word equation.
2) Write a formula equation by substituting correct
formulas for the names of the reactants and products.
3) Using coefficients, balance the formula equation
according to the law of conservation of mass.
– Balance the different types of atoms one at a time.
– First balance atoms of elements that appear only
once on each side.
– Balance polyatomic ions that appear on both sides
as single units.
– Balance H and O atoms after atoms of other
elements have been balanced.
4) Count atoms to be sure the equation is balanced.
Balancing a Formula Equation
• hydrogen gas reacts with chlorine gas to
produce hydrogen chloride gas
• _?_ H2(g) + _?_ Cl2(g)  _?_ HCl(g)
•
H2(g) +
Cl2(g)  2 HCl(g)
Practice #1-
Balance the following formula equations.
__CaF2 + __Na2S  __CaS + __ NaF
__FeS + __ AlPO4  __Fe3(PO4)2 + __Al2S3
__Na + __Cl2  __NaCl
__H2 + __O2  __H2O
__C2H4 + __O2  __CO2 + __H2O
__HBr + __NaOH  __NaBr + __H2O
__Na2SO4 + __AlPO4  __Na3PO4 + __Al2(SO4)3
__N2 + __O2  __N3O7
__FePO4 + __CaSO4  __Fe2(SO4)3 + __Ca3(PO4)2
__CuBr2 + __NaF  __CuF2 + __NaBr
Balanced Formula Equation
__CaF2 + __Na2S  __CaS + __ NaF
CaF2 + Na2S  CaS + 2 NaF
1:1:1:2
__FeS + __ AlPO4  __Fe3(PO4)2 + __Al2S3
3 FeS + 2 AlPO4  Fe3(PO4)2 + Al2S3
3:2:1:1
__Na + __Cl2  __NaCl
2 Na + Cl2  2 NaCl
2:1:2
__H2 + __O2  __H2O
2 H2 + O2  2 H2O
2:1:2
__C2H4 + __O2  __CO2 + __H2O
C2H4 + 3 O2  2 CO2 + 2 H2O
1:3:2:2
Practice
__HBr + __NaOH  __NaBr + __H2O
HBr + NaOH  NaBr + H2O
1:1:1:1
__Na2SO4 + __AlPO4  __Na3PO4 + __Al2(SO4)3
3 Na2SO4 + 2 AlPO4  2 Na3PO4 + Al2(SO4)3 3:2:2:1
__N2 + __O2  __N3O7
3 N2 + 7 O2  2 N3O7
3:7:2
__FePO4 + __CaSO4  __Fe2(SO4)3 + __Ca3(PO4)2
2 FePO4 + 3 CaSO4  Fe2(SO4)3 + Ca3(PO4)2 2:3:1:1
__CuBr2 + __NaF  __CuF2 + __NaBr
CuBr2 + 2 NaF  CuF2 + 2 NaBr
1:2:1:2
Practice Problems
• Do the following practice problems from the
textbook:
practice #1 & #2 on page 272
practice #1 (a, b, c) on page 274
section review #2, #3, #4, & #5 on
page 274
Practice Problems page 272
1a)
Mg + HCl  MgCl2 + H2
Mg + 2 HCl  MgCl2 + H2
1b)
HNO3 (aq) + Mg(OH)2 (s)  Mg(NO3)2 (aq) + H2O (l)
2 HNO3 (aq) + Mg(OH)2 (s)  Mg(NO3)2 (aq) + 2 H2O (l)
2)
Ca(s) + H2O(l)  Ca(OH)2 (aq) + H2 (g)
Ca(s) + 2 H2O(l)  Ca(OH)2 (aq) + H2 (g)
Practice Problems page 274
1a)
Na (s) + Cl2 (g)  NaCl (s)
2 Na (s) + Cl2 (g)  2 NaCl (s)
1b)
Cu (s) + AgNO3 (aq)  Cu(NO3)2 (aq) + Ag (s)
Cu (s) + 2 AgNO3 (aq)  Cu(NO3)2 (aq) + 2 Ag (s)
1c)
Fe2O3 (s) + CO (g)  Fe (s) + CO2 (g)
Fe2O3 (s) + 3 CO (g)  2 Fe (s) + 3 CO2 (g)
Section Review page 274
2)
H2SO4 (aq) + NaOH (aq)  Na2SO4 (aq) + H2O (l)
H2SO4 (aq) + 2 NaOH (aq)  Na2SO4 (aq) + 2 H2O (l)
3a)
solid potassium plus liquid water produce
aqueous potassium hydroxide and hydrogen gas
3b)
solid iron metal plus chlorine gas yields
solid iron (III) chloride
4)
H2S (g) + O2 (g)  SO2 (g) + H2O (g)
2 H2S (g) + 3 O2 (g)  2 SO2 (g) + 2 H2O (g)
Section Review page 274
5)
VO + Fe2O3  V2O5 + FeO
2 VO + 3 Fe2O3  V2O5 + 6 FeO
QUIZ #1- Balancing chemical equations
Balance the following formula equations.
1-
___C3H8 + ___O2  ___CO2 + ___H2O
2-
___Al2(SO4)3 + ___Fe3(PO4)2  ___AlPO4 + ___FeSO4
3-
___Na + ___Cl2  ___NaCl
4-
___N2 + ___O2  ___N3O7
5-
___NaNO3 + ___Al2(CO3)3  ___Na2CO3 + ___Al(NO3)3
Types of Chemical Reactions
synthesis reaction- also known as a
composition reaction, two or more
substances combine to form a new
compound.
A + X  AX
Could be called the ”Boy Meets Girl” reaction.
Types of Chemical Reactions
decomposition reaction- a single
compound undergoes a reaction that
produces two or more simpler
substances.
AX  A + X
The “Boy Loses Girl” reaction.
Types of Chemical Reactions
single-displacement reaction- also
known as a replacement reaction, one
element replaces a similar element in a
compound.
A + BX  AX + B
The “Boy Loses Girl to Best Friend” reaction.
Types of Chemical Reactions
double-displacement reaction- also
known as a double replacement reaction,
the ions of two compounds exchange
places in an aqueous solution to form
two new compounds.
AX + BY  AY + BX
The “Best Friends Trade Girlfriends” Reaction.
Types of Chemical Reactions
combustion reaction- a substance
combines with oxygen, releasing a large
amount of energy in the form of light and
heat
A + O2  AO + fire
The “Where There’s Smoke There’s Fire” reaction.
Reaction Types Summary
Synthesis
A + X  AX
Decomposition
AX  A + X
Single Displacement
A + BX  AX + B
Double Replacement
AX + BY  AY + BX
Combustion
A + O2  AO + fire
QUIZ #2-
Balance the following formula equations then identify
the reaction type.
__Na + __Br2  __NaBr
reaction type=
__Fe2O3  __Fe + __O2
reaction type=
__CuI + __F2  __CuF + __I2
reaction type=
__FeSO4 + __Ca3(PO4)2  __Fe3(PO4)2 + __CaSO4
reaction type=
__C4H8 + __O2  __CO2 + __H2O (fire)
reaction type=
QUIZ #2-
Balance the following formula equations then identify the reaction type.
__Na + __Br2  __NaBr
2 Na + Br2  2 NaBr
synthesis (composition)
__Fe2O3  __Fe + __O2
2 Fe2O3  4 Fe + 3 O2
decomposition
__CuI + __F2  __CuF + __I2
2 CuI + F2  2 CuF + I2
single replacement (single displacement)
__FeSO4 + __Ca3(PO4)2  __Fe3(PO4)2 + __CaSO4
3 FeSO4 + Ca3(PO4)2  Fe3(PO4)2 + 3 CaSO4
double replacement (double displacement)
__C4H8 + __O2  __CO2 + __H2O (fire)
C4H8 + 6 O2  4 CO2 + 4 H2O (fire)
combustion
Types of Chemical Reactions
synthesis reaction- also known as a
composition reaction, two or more
substances combine to form a new
compound.
A + X  AX
Journal Investigation- Synthesis Reaction
1) Get a strip of magnesium ribbon and an iron crucible from
the front.
2) Roll the magnesium strip into a loose ball.
3) Weigh & record the mass of the magnesium & crucible on a
scale.
4) Heat the crucible and magnesium using your burner until
the magnesium begins to glow. Turn off the burner.
5) Allow the crucible to cool at least five minutes.
6) Weigh and record the new mass of the crucible &
magnesium oxide product.
7) Add three or four drops of tap water to the crucible. Waft
the gas produced to attempt to smell the odor of ammonia.
Safety Precautions
Burner & equipment become very hot. DO NOT touch. Handle
with crucible tongs.
Eye protection MUST be worn due to possible sparks in the
crucible.
Safety apron is to be worn to protect skin & clothing.
Use a wafting technique when trying to detect ammonia smell.
Rinse & dry the cool crucible after lab is finished.
Journal Investigation- Synthesis Reaction
ANALYSIS
1) Using the recorded masses, show how this proves a
synthesis reaction occurred.
2) The magnesium (Mg) combined with oxygen (O2) in the
air to form a magnesium oxide (MgO) product. Write a
balanced formula equation for this reaction.
3) When you added water, you should have smelled
ammonia (NH3). The formula equation for this reaction
would be Mg3N2 + H2O  Mg(OH)2 + NH3. Balance this
formula equation.
4) Where did the nitrogen come from to form the Mg2N3
as another product of this synthesis reaction?
Types of Chemical Reactions
decomposition reaction- a single
compound undergoes a reaction that
produces two or more simpler
substances.
AX  A + X
Lab Investigation- Decomposition Reaction
1) Get a test tube with 5 – 10 mL of fresh hydrogen
peroxide (H2O2) from the rack in the front of the room.
2) Add a match-head size amount of manganese dioxide
(MnO2) to the test tube to act as a catalyst (a substance
that speeds up a reaction without becoming part of it).
3) Observe the hydrogen peroxide for signs of a chemical
reaction.
4) While the reaction is still taking place, set the end of a
wooden splint on fire then blow it out.
5) While the splint is still glowing, lower it into the top of
the test tube without touching the liquid. Observe the
result. You can repeat this step several times until the
reaction in the test tube stops.
Lab Investigation- Decomposition Reaction
ANALYSIS
1) Use your textbook to find the definition of a catalyst. Write
the definition in the log.
2) What was the indication in the test tube that a chemical
reaction was taking place?
3) Hydrogen peroxide decomposed into oxygen gas and liquid
water. Write the balanced formula equation for this
reaction.
4) What test was used to demonstrate that oxygen gas was a
product of the reaction?
5) Write a balanced formula equation for the reaction between
the carbon in the wood and the oxygen gas being produced.
What type of chemical reaction is this?
Types of Chemical Reactions
single-displacement reaction- also
known as a replacement reaction, one
element replaces a similar element in a
compound.
A + BX  AX + B
Lab Investigation- Single Replacement Reaction
1) Get a small beaker with 20-25 mL. of silver nitrate (AgNO3).
BE CAREFUL- silver nitrate will cause burn on your skin &
clothing.
2) Record in your journal the color of the silver nitrate solution.
3) Get a penny from your instructor.
4) Gently lower the penny into the beaker of silver nitrate
making sure there is no splash.
5) Record observation of the penny in your journal for 10
minutes at 1 minute intervals.
6) Use a piece of tape to identify your beaker & penny. Place
the beaker in the fume hood overnight.
7) Record your observations after 24 hours. Be sure to include
the color of the liquid in the beaker.
Lab Investigation- Single Replacement Reaction
ANALYSIS
1) What were the indications that a chemical reaction
had taken place?
2) What were the products of the single replacement
reaction between copper (Cu) and silver nitrate
(AgNO3)? (Assume the product contains the copper
I ion.)
3) Write the balanced formula equation for the
reaction between copper and silver nitrate.
4) Based on your observations, which element, copper
or silver would appear higher on an activity series
of metals? Why?
Types of Chemical Reactions
double-displacement reaction- also
known as a double replacement reaction,
the ions of two compounds exchange
places in an aqueous solution to form
two new compounds.
AX + BY  AY + BX
Lab Investigation- Double Replacement Reaction
1) Get a test tube with 5 mL. of silver nitrate (AgNO3).
BE CAREFUL- silver nitrate will cause burns on your
skin & clothing.
2) Record in your journal the color of the silver nitrate
solution.
3) Get a test tube of sodium chloride (NaCl) solution.
Record your observations of the solution.
4) Gently pour the sodium chloride into the test tube
of silver nitrate making sure there is no splash.
5) Record your observation of the mixtures of the two
aqueous solutions.
6) Take the test tubes to the front for disposal.
Lab Investigation- Double Replacement Reaction
ANALYSIS
1) What were the indications that a chemical
reaction had taken place?
2) What were the products of the double
replacement reaction between sodium
chloride (NaCl) and silver nitrate (AgNO3)?
3) Which of these products is the precipitate?
4) Write the balanced formula equation for the
reaction between aqueous sodium chloride
and aqueous silver nitrate.
Types of Chemical Reactions
combustion reaction- a substance
combines with oxygen, releasing a large
amount of energy in the form of light and
heat
A + O2  AO + fire
Just for Fun- The Kandy Killer
This will be a demonstration ONLY.
1) We will be heating potassium chlorate (KClO3).
This will cause it to undergo a decomposition
reaction that produces potassium chloride and
oxygen.
2) A glowing splint will be used to confirm that
oxygen is being produced.
3) Candy will be dropped into the test tube. A rapid
chemical reaction should be seen. YEA!!!
Practice Problems
section review
problems:
#1 through #5 on
page 284 of the
textbook.
Section Review page 284
1- List 5 types of reactions identified in this chapter.
synthesis
decomposition
single displacement (replacement)
double displacement (replacement)
combustion
2abcd-
N2 + 3H2  2 NH3
2Li + 2H2O  2LiOH + H2
2NaNO3  2NaNO2 + O2
2C6H14 + 19O2  12CO2 + 14H2O
synthesis
single displacement
decomposition
combustion
3a-
QUIZ #3-
Chemistry Chapter 8 Test Review
Balance the following equations & identify the reaction type.
1) __Ca(NO3)2 + __Na3PO4  __Ca3(PO4)2 + __NaNO3
reaction type:
2) __C4H8 + __O2  __CO2 + __H2O + fire
reaction type:
3) __H2 + __Br2  __HBr
reaction type:
4) __K + __HBr  __KBr + __H2
reaction type:
5) __CaCO3  __CaO + __CO2
reaction type:
Activity Series of the Elements
• The activity of an element describes how it
can react under specific conditions
• An activity series is a list of elements
organized according to the ease with which
elements undergo certain chemical reactions.
Activity Series of Metals
Most reactive:
Li
Rb
K
Ba
Sr
Ca
Na
React with cold water and acids,
replacing hydrogen.
React with oxygen forming oxides
Activity Series of Metals
2nd most reactive set:
Mg
Al
Mn
Zn
Cr
Fe
Cd
React with steam (but not cold
water) and acids, replacing
hydrogen. React with oxygen,
forming oxides.
Activity Series of Metals
3rd most reactive set:
Co
Ni
Sn
Pb
Do not react with water.
React with acids, replacing hydrogen.
React with oxygen, forming oxides.
Activity Series of Metals
4th most reactive set:
H2
Sb
Bi
Cu
Hg
React with oxygen, forming oxides.
Activity Series of Metals
Least reactive set:
Ag
Pt
Au
Fairly unreactive, forming oxides only
indirectly.
Activity of Halogen Non-metals
The following halogens will replace any other
halogen below it in a single replacement
reaction.
F2
Cl2
Br2
I2
Practice Problems
• Use table 3 on
page 286 of the
textbook to
answer Practice
Problems #1
through #3 on
page 287.
Practice problems page 287
1a-
____ Cr + ____H2O (l)  ?
cannot occur- Cr will not react with water, only steam
b-
____Pt + ____O2  ?
cannot occur-Pt does not form oxides directly
c-
____Cd + 2 HBr  ? (HBr is an acid)
can occur Cd reacts with acids to form hydrogen
Cd + 2 HBr  CdBr2 + H2
d-
____Mg + ____H2O(g)  ? H2O (g) is steam
can occur, Mg will react with steam to form hydrogen
Mg(s) + 2 H2O(g)  Mg(OH)2 (aq) + H2 (g)
Practice Problems page 287
2- Identify the element that replaces hydrogen from acids
but does not replace tin from its compounds.
Lead (Pb) replaces hydrogen from acids, but is below tin
(Sn) in the activity series so it cannot replace tin (Sn).
3- According to table 3, what is the most active transition
metal?
As you go down the activity series of metals,
manganese (Mn) is the first transition metal in the list,
so it is the most reactive transition metal.
QUIZ #4-
Chemistry Chapter 8 Test Review
Use the activity series to determine if the following reactions
are possible.
1) Sb + HCl (an acid)
2)
K + ZnCl2 
3) 2 HF + Cl2 
4) 2 H2O (l) + 2 Na 
5) MgBr2 + Cl2 
Chemistry Chapter 8 Test
25 multiple choice questions:
 definition of a precipitate
 identify diatomic elements when used in chemical
equations
 rules for balancing equations
 identify a word equation
 symbols used in equations (eg. aq)
 determine coefficients needed to balance equations
 identify reaction types by definition & balanced formula
equations
 definitions of activity & activity series and how they are
used
Honors Chemistry Chapter 8 Test
35 multiple choice questions:
 chemical reactions & law of conservation of mass
 indicators of chemical reactions
 definition of a precipitate and symbols used in equations
 identify a word equation & a formula equation
 diatomic elements & how they are written in an equation
 Identify coefficients needed to balance formula equations
 rules for balancing formula equations
 reaction types by definition & balanced equations
 identifying & predicting products of reactions
 definitions of activity & activity series
 use activity series to predict products formed
Honors Chemistry Chapter 8 Test
1 short answer question:
 When balancing a formula equation, why must the formula
subscripts remain unchanged?
1 essay question:
 Consider an equation. How does the equation violate the
law of conservation of mass? How can the equation be
rewritten to conform to the law of conservation of mass?
3 problems:
 Write a balanced formula equation for a synthesis reaction
when given the reactants & product.
 Use an activity series to predict if a reaction can occur. If
yes, write the balanced formula equation. (2 of these)