1. Ch 8.1 Balancing Equations
Standard 3.a.: Students know how to describe chemical equations by writing balanced equations.
Content Objective: We will know how to write word, formula, and chemical equations for chemical reactions and balance chemical equations.
Language Objective: I will write word, formula, and chemical equations for chemical reactions and balance chemical equations.

2. Indications of a Chemical Reaction
Evolution of energy as heat and light.
Production of a gas
Formation of a precipitate
Color Change

3. Characteristics of Chemical Equations
The equation must represent known facts.
The equation must contain the correct formulas for the reactants and products.
The law of conservation of mass must be satisfied.

4. Chemical Reactions
Chemical equations give information in two major areas:
1. Reactants and products of the reaction.
2. Coefficients of a balanced chemical equation tell us the amount of the substances involved.
Example: 2H2 (g) + O2 (g)  2H2O (g)
Review: Reactants are on the left side of the arrow, and the products are on the right side. The arrow means “yields”, or “to produce”.

5. Balancing Chemical Equations
Why do you have to balance a chemical equation?
Law of Conservation of Matter (or Mass)
During a chemical reaction, atoms are either joined, separated, or rearranged. The number and type of each atom stays the same.
How do you balance a chemical equation?
Coefficients 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.

6. 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

7. 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

8. 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

9. 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
Polyatomic ions 2 3 1 3
start over 2 2 2 1
Fix it 2 1 3

10. Aluminum + Oxygen  Aluminum Oxide
Example
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. Write word, formula, and chemical equations for this reaction.
Aluminum + Oxygen  Aluminum Oxide
Al(s) + O2(g)  Al2O3(s)
4Al(s) + 3O2(g)  2Al2O3(s)

11. Homework
8.1 page 274 #1-3 and page 290 #1-2, 13

12. Ch 8.2: Five 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 “H,N,O,F,Cl,Br,I” elements are diatomic when alone!!
Remember to balance the equation after you write the products.
one compound + AX
A X H2 O2 O2
KCl

13. General Types of Reactions
2) __________: (sometimes called Combination)
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  ______
Synthesis
two substances
one compound + A X AX
AlCl3
Pb(OH)2

14. General Types of Reactions (Continued)
3) _________________: Reacts with oxygen gas!!!
A reaction between a Carbon/Hydrogen with _____ always produces the same… ________ + ________
This reaction is too easy!! Don’t miss it!
General Form: CxHy + O2  ____ + ____
Examples: 2C2H O2  _______ + _______
C7H6O O2  _______ + _______
Combustion O2
CO2
H2O
CO2
H2O
4CO2
2H2O
7CO2
3H2O

15. General Types of Reactions (Continued)
4) _____________ Displacement:
A reaction between ____ ______________ and ___ ____________ that produces a different _____________ and ______________.
General Forms: ____ + __  ____ __
____ + __  ____ __
Single
one compound
one element
compound
element + AX Y AY X AX B BX A +

16. General Types of Reactions (Continued)
5) _______________ Displacement:
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: ____ + ____  ____ + ____
A solid produced during a chemical reaction is called a precipitate.
Examples: CaCl2 (aq) AgNO3 (aq)  _________ + ________
NaOH (aq) + HCl (aq)  ________ + ________
Double
two compounds
two compounds
insoluble
AX(aq)
BY(aq)
AY(aq)
BX(s) + +
Ca(NO3)2
AgCl (s)
(aq)
NaCl
(aq)
H2O (l)

17. Double Displacement Reaction

18. pg 291 #27 (write formulas, balance, and then classify!)
Homework
8.2 pg 284 #1-2
pg 291 #27 (write formulas, balance, and then classify!)

19. Types of Reactions and Activity Series
Ch 8.2 and 8.3 Notes
Types of Reactions and Activity Series

20. Standard 3.a.: Students know how to describe chemical equations by writing balanced equations.
Content Objective: We will know how to determine products for the five types of reactions.
Language Objective: I will write the products of the chemical reaction and then balance the chemical reaction.

21. Making Synthesis Reactions
Metals with nonmetals  ionic compounds
Mg + O2  MgO
Nonmetals w/ nonmetals  covalent compounds
C + O2  CO2
Metal Oxides react with water to form Hydroxides
CaO + H2O  Ca(OH)2
Nonmetal Oxides react with water to form acids
SO2 + H2O  H2SO3

22. Decomposition Decomposition of Binary Compounds HgO  Hg + O2
Decomposition of Metal Carbonates
CaCO3  CaO + CO2
Decomposition of Metal Hydroxides
Ca(OH)2  CaO + H2O
Decomposition of Metal Chlorates
KClO3  KCl + O2
Decomposition of Acids
H2CO3  CO2 + H2O

23. Remember, these ALWAYS produce CO2 and H2O!
Combustion
Remember, these ALWAYS produce CO2 and H2O!

24. Single Displacement
The element that is trying to replace the other must be more reactive than the one it is replacing.
You must use the Activity Series to see if the reaction will happen. Page 286 Table 3
The Higher up it is = the more reactive it is.
Elements from Li to Na can displace hydrogen in water to form a metallic hydroxide and H2 gas.

25. 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

26. Remember the Activity Series!
Single Displacement
Remember the Activity Series!
Metals Replace Metals
Al + Pb(NO3)2  Pb + Al(NO3)3
Metals Replace Hydrogen in Water
Na + H2O  NaOH + H2
Metals Replace Hydrogen in Acid
Mg + HCl  H2 + MgCl2
Halogens replace halogens below them

27. Double Displacement
Switch the compounds and make sure the new compounds are balanced.
KI + Pb(NO3)2  PbI2 + KNO3
They will always react and switch, no activity series needed!

28. Once you have solved for the products of the reaction, you must then BALANCE the reaction!

29. Standard 3.a.: Students know how to describe chemical equations by writing balanced equations.
Content Objective: We will know how to determine products for the five types of reactions.
Language Objective: I will write the products of the chemical reaction and then balance the chemical reaction.

30. (solve for products, balance, and classify the reactions.)
Homework
8.2 page 284 #4
(solve for products, balance, and classify the reactions.)
8.3 page 287 #2-3
(In #2, predict which reactions will occur using activity series, then in #3, solve for the products for the ones that will occur and then balance.)