1. Balancing Chemical Equations and Types of Chemical Reactions
Boon Chemistry

2. Objectives
I can compare and contrast different types of chemical reactions.
I can define and identify a balanced chemical equation.
I can balance simple chemical equations.

3. Parts of a Chemical Reaction
Reactants
Products
Cu (s) + 2 AgNO3 (aq) → Cu(NO3)2 (aq) + 2 Ag (s)
Letters in parentheses show the state of matter.
Coefficients (numbers) in front of a chemical formula show “how many.”
Reaction:
The arrow separates the reactants and products.

4. Balancing a Chemical Reaction Equation
Atoms are not created or destroyed during a chemical reaction.
Scientist know that there must be the same number of atoms on each side of the arrow.

5. __Cu + __ AgNO3 → __Cu(NO3)2 + __ Ag
Is it balanced?
__Cu + __ AgNO3 → __Cu(NO3)2 + __ Ag
Cu = Cu =
Ag = Ag =
NO3 = NO3 =

6. Balancing a Chemical Reaction Equation
To balance the chemical equation, you must add coefficients to the different parts of the equation.
Cu (s) + 2 AgNO3 (aq) → Cu(NO3)2 (aq) + 2 Ag (s)

7. Steps for Balancing Chemical Reaction Equations
Determine number of atoms for each element for the reactants and products separately.
Try to add coefficients to the equation to get the same number of atoms on each side.
Note: Coefficients multiply the atoms in the compound. Keep the compound formulas the same. Do not change subscripts.
Hint: Balance anything that is not hydrogen or oxygen first. Then balance hydrogen. Balance oxygen last.

8. Why do we balance Chemical Reactions?
Focus Questions:
How are the two reactions the same? How are they different? Why?
If you wanted to do these reactions at home, what would you need to know?

9. Law of Conservation of Mass
Matter cannot be created or destroyed in a chemical reaction
The number of atoms on the reactant side must equal the atoms of the products + H2 
H2O O2
(g)
(l) O H O H H H O
Unbalanced!
Balanced!

10. Balanced Chemical Equations
A chemical equation is “balanced” when there are the same number of atoms of each element on both sides of the arrow.
NaHCO3 (s) + HC2H3O2 (aq) èNaC2H3O2 (aq) + CO2 (g) + H2O (l)
Is it balanced?
Reactants
Products
Na = 1
H = 5
C = 3
O = 5

11. Is it balanced? Practice
Determine the number of atoms of each element in the reactants and products. Then, state whether the equation is balanced.
P4 + O2 → P2O5
C3H8 + O2 → CO2 + H2O
Ca2Si + Cl2 → CaCl2 + SiCl4
Si + CO2 → SiC + SiO2
Not balanced.
Not balanced.
Not balanced.
Not balanced.

12. + 2 2 H2 H2O O2 Balancing Equations  (g) (l) H = O = 2 4 H = O = 2 4
coefficient 2 2 H2 
H2O + O2
(g)
(l)
H =
O = 2 4
H =
O = 2 4 2 1 2
Only the coefficients can be changed!

13. Balancing Tips
Always balance non-Oxygen’s & Hydrogen’s first (ex. Chlorine)
Then balance Hydrogens
Balance Oxygens Last

14. Balancing Practice! P4 + O2 → P2O5 Ca2Si + Cl2 → CaCl2 + SiCl4
Si + CO2 → SiC + SiO2
2 Si + CO2 → SiC + SiO2
C3H8 + O2 → CO2 + H2O
C3H8 + 5 O2 → 3 CO2 + 4 H2O

15. Overview of Major Chemical Reaction Types
Synthesis
Decomposition
Single-Replacement
Double-Replacement
Combustion

16. 1. Synthesis Reactions + H2 H2O O2  (g) (l) O O O O
Two substances combine to make one
Synthesis means “to make” + H2 
H2O O2
(g)
(l) O O H H O H O H

17. SYNTHESIS
A + B  AB
Na + Cl2  NaCl

18. 2. Decomposition Reactions
One substance breaks down into 2
Decomposition means “to break down” or “decay” +
NH3  H2
(g)
(l) N2 H H H H N N H H

19. Decomposition
AB  A + B
NaCl  Na + Cl2

20. one element replaces another in a compound
3. SINGLE REPLACEMENT
one element replaces another in a compound
AB + C  AC + B

21. Single Replacement Reaction

22. Single Replacement
AB + C  AC + B or CB + A
NaBr + Cl2  NaCl + Br2

23. Both elements in two compounds switch places
4. DOUBLE REPLACEMENT
Both elements in two compounds switch places
AB + CD  AD + CB

24. NaBr + Pb2S3  Na2S + PbBr3 Double Replacement KOH + BaSO4
K2SO4 + Ba(OH)2
KOH + BaSO4

25. + + + 5. Combustion Reactions CH4 H2O O2 CO2 C2H4 H2O O2 CO2 C6H12O6
A hydrocarbon reacts with oxygen gas to produce carbon dioxide and water vapor
Combustion means to “burn in oxygen” +
CH4 
H2O O2
CO2 +
C2H4 
H2O O2
CO2 +
C6H12O6 
H2O O2
CO2