1. Ch. 8 Notes -- Chemical Reactions
Chemical equations give information in two major areas:
1. _____________ and ______________ of the reaction.
2. Coefficients of a balanced chemical equation tell us the ______ of the substances involved.
Example of a Balanced Chemical Equation: 2H2 (g) + O2 (g)  2H2O (g)
Review: Reactants are on the ______ side of the arrow, and the
products are on the __________ side. The arrow means “________”,
or “reacts to produce” when read aloud.
From our example, hydrogen reacts with oxygen in a ___:___ ratio.
The coefficients represent either the number of _________ or molecules present.
The coefficients can also represent _________ if the substances are gases.
(1 mole = 6.02 x 1023 molecules, GFM= 22.4 Liters)
Reactants
products
amount
left
right
yields
2 1
moles
liters

2. Common Symbols used in Chemical Equations
(See Table 8.1)
+ = used to separate 2 reactants or 2 products from each other
→ = “yields” or “reacts to produce”
= _____________ reaction (like a rechargeable battery)
(s) (l) (g) (aq) = phase of matter: (solid, liquid, gas, or “aqueous”)
= ___________ supplied to the reaction
MnO2 = a catalyst, (in this case, MnO2), is used to ________ ____ the reaction.
= _______ given off as a product
= ______ precipitate produced
reversible
heat
speed up
gas
solid

3. Decoding Common Chemical Equation Symbols
Practice Problems: Describe the following reactions using complete sentences.
a) NaHCO3 (s) + HCl (aq)  NaCl (aq) + H2O (l) + CO2
b) H2SO4 (aq) + BaCl2 (aq)  HCl (aq) + BaSO4 (s)
c) Write a chemical equation from the following description: “Sodium plus bromine, when heated, reacts to produce solid sodium bromide.”
Solid
sodium bicarbonate
plus
aqueous
hydrochloric acid
yields
aqueous
sodium chloride
plus
water
plus
carbon dioxide gas.
Aqueous
sulfuric acid
plus
aqueous
barium chloride
yields
aqueous
hydrochloric acid
plus
solid
barium sulfate. Na
(s) +
Br2 
NaBr (s)
(l)

4. Balancing Chemical Equations
Why do you have to balance a chemical equation?
Law of Conservation of Matter (or Mass): “Matter is neither ____________ nor _______________ in chemical reactions.”
During a chemical reaction, atoms are either _________, ______________, or rearranged. The _____________ and type of each atom stays the same.
How do you balance a chemical equation?
__________________ are placed in front of the substances involved in the chemical reaction to get the same number of atoms of each element on both sides of the equation. This number will multiply the number of atoms there are in a formula.
created
destroyed
joined
separated
number
Coefficients

5. Rules for Balancing Chemical Equations
(1) Coefficients can only be placed ___ _________ of a chemical formula.
Practice Problems: How many atoms of each type are indicated in
the following compounds?
(a) 2 (NH4)3PO N= ___ H= ___ P= ___ O= ___
(b) 4 KC2H3O K= ___ C= ___ H= ___ O= ___
(c) 3 Ca(NO3) Ca= ___ N= ___ O= ___
in front 6 24 2 8 4 8 12 8 3 6 18

6. Rules for Balancing Chemical Equations
(2) You cannot change a ________________!!
Example : H O2  H2O
To balance oxygen, you cannot change water’s formula to_________!
(3) You cannot place the coefficient in the ______________ of a formula!!
Example : Al N2  AlN
To balance nitrogen, you cannot put a 2 in the middle to make _______.
(4) Reduce the coefficients to the simplest ____________ ___ ratio.
Example: H O2  4H2O can be reduced to…
__H2 + __O2  __H2O
subscript 2 2
H2O2
middle 2 2
Al2N
whole # 2 1 2

7. Rules for Balancing Chemical Equations
(5) Get rid of any ____________! Coefficients must be _________ #’s
You can’t have a _______________ of a molecule or atom!
Example: 1H ½O2  1H2O changes to…
__ H __O2  __H2O
fractions
whole
fraction
2 x ( ) 2 1 2

8. Balancing Equations: “Helpful Hints”
a) Balance elements that appear in more than one compound ________.
___(NH4)2CO3  ___NH ___CO ___H2O
b) Balance _____ “___________” as though it were one item as long as the ion stays together as a group on each side of the yields arrow.
___Al ___CuSO4  ___Al2(SO4) ___Cu
c) If you can’t seem to get it balanced, _________ _________ and begin with a different element the next time, or put a “2” somewhere and then try again.
___Li ___H2O  ___LiOH ___H2
This is what I’ll constantly be telling you to do if you are stuck and you need my help... “Pick an element to balance. How many are on the left side? How many are on the right side? ________ ____!”
___Fe(OH)3  ___Fe2O ___H2O
last 1 2 1 1
ion
chunks 2 3 1 3
start over 2 2 2 1
Fix it 2 1 3

9. Balancing Equations: “Helpful Hints”
e) My goofy “balancing song” may help:
“If there’s a ___ on the left and a ___on the right, you put a ___ on the
left and a ___ on the right, (makin’ money!)”
___Al ___O2  ___Al2O3
f) If you see only C’s H’s and O’s, balance them in this order: C, H, O.
___C2H ___O2  ___CO ___H2O 2 3 3 2 4 3 2
2 x ( ) 1
5/2 2 1 2 5 4 2

10. Five General Types of Reactions
Decomposition
1) ________________________:
A reaction that breaks apart ______ ______________ into simpler substances, (usually two elements or an element and a smaller compound.)
General Form: _____  ___ + ___
Examples: H2O  _____ + _____
KClO3  _____ + _____
Remember that “HONClBrIF” elements are diatomic when alone!!
one compound + AX
A X H2 O2 O2
KCl

11. Categories of Decomposition (and Composition ) Reactions
CaO
CO2
a) carbonates  metallic oxide + CO CaCO3  _____ + _____
b) chlorates  metallic chloride + O NaClO3  _____ + _____
c) hydroxides  metallic oxide + H2O Mg(OH)2  _____ + _____
d) oxy acids  nonmetal oxide + H2O H2SO4  _____ + _____
e) binary compounds  2 elements NaCl  _____ + _____
Every time you try to write the formula for a new compound, you must look up the ___________ of the ions and ___________ them if they are different!!
Balance it _________ you get all the correct formulas written first!
Don’t forget about the HONClBrIF’s!
NaCl O2
MgO
H2O
SO3
H2O Na
Cl2
charges
cross
AFTER

12. General Types of Reactions (Continued)
Composition
2) _______________: (sometimes called “Combination” or “Synthesis”)
A reaction of _____ __________________, typically a metal and a nonmetal to form ______ ______________.
It is the opposite of decomposition. (The same categories of reactions from above apply, just in reverse.)
General Form: ___ ___  _____
Examples: Al Cl2  _______
PbO + H2O  ______
two substances
one compound + A X AX
AlCl3
2 elements 
binary compound
Pb(OH)2
metallic water
oxide
 hydroxide

13. General Types of Reactions (Continued)
3) _____________ Replacement:
A reaction between ____ ______________ and ___ ____________ that produces a different _____________ and ______________.
General Forms: ____ + __  ____ __
____ + __  ____ __
The element that is trying to replace the other must be ________ _______________ than the one it is replacing.
You must use the Activity Series to see if the reaction will happen.
Table J _________ ___ = more reactive
Elements from ____ to ____ can displace hydrogen in water to form a metallic hydroxide and H2 gas.
Single
one compound
one element
compound
element + AX Y AY X AX B BX A +
more
reactive
Higher up Li Na

14. Activity Series

15. Single Replacement Reactions
Examples:
NaCl F2  _____ + _____
FeCl K  _____ + _____
HCl Zn  _____ + _____
HCl Au  _____ + _____
H2O Na  _____ + _____
H2O Fe  _____ + _____
AgNO3 + Cu  _____ + _____
NaF
Cl2
KCl Fe
ZnCl2 H2
no reaction H2
NaOH
H(OH)
no reaction
CuNO3 Ag

16. General Types of Reactions (Continued)
4) _______________ Replacement: (sometimes called “Ionic”)
A reaction between _____ ________________ that are dissolved in water that produces _____ ________________ , one of which is ________________.
Water or a gas may be one of the two compounds being produced.
General Form: ____ + ____  ____ + ____
You must use the Solubility Chart to see which product is the precipitate.
Table A-7 on p ___ or _____= precipitate
Examples: CaCl2 (aq) AgNO3 (aq)  _________ + ________
NaOH (aq) + HCl (aq)  ________ + ________
Double
two compounds
two compounds
insoluble
AX(aq)
BY(aq)
AY(aq)
BX(s) + + I sS
Ca(NO3)2
(aq)
AgCl
(aq)
NaCl
H2O (l)

17. Double Replacement Reaction

18. General Types of Reactions (Continued)
5) _________________:
A reaction between a Carbon/Hydrogen (and sometimes Oxygen) _________________ with _____.
The products are always the same… ________ + ________
This reaction is too easy!! Don’t miss it!
General Form: CxHy + O2  ____ + ____
Examples: C2H O2  _______ + _______
C7H6O O2  _______ + _______
Combustion O2
compound
CO2
H2O
CO2
H2O
CO2
H2O
CO2
H2O

19. Writing Net Ionic Equations for Double Replacement Reactions
A “net ionic equation” only shows the _________ that were used to make the precipitate.
Some ions were always dissolved in water. These are called “________________ ions”. (They don’t do anything, so we can ignore them.)
Example: CaCl2 (aq) + 2AgNO3 (aq)  Ca(NO3)2 (aq) + 2AgCl (s)
Ionic Equation Written as Ions Dissolved in Water:
___ (aq) + ___ (aq) + ___ (aq) + _____ (aq)  ___ (aq) + _____ (aq) + _________ (s)
Cancel out the spectator ions, and you are left with the Net Ionic Equation!
________ _________  __________
ions
spectator
Ca+2
2Cl−
2Ag+
2NO3 −
Ca+2
2NO3 −
2AgCl
2Cl−(aq)
2Ag+(aq)
2AgCl(s)

20. Writing Net Ionic Equations for Double Replacement Reactions
Practice Problem: Write the net ionic equation for the following reaction.
K2CO3 (aq) Ba(NO3)2 (aq)  _________ + _________
Net Ionic Equation = ____________________________________
KNO3
(aq)
BaCO3
CO3 −2 (aq) +
Ba+2 (aq)
BaCO3