1. Balancing Equations and Classifying Chemical Reactions
What are the parts of a chemical equation?
What do these parts represent?
Why do we balance chemical equations?
How do we balance chemical equations?
How can we use a chemical equation to identify the type of chemical reactions?

2. What are the parts of a chemical equation?
Let’s examine this chemical equation and learn what each part means:
2H O2 → 2H2O
Identify: Reactants
products
subscript
coefficient

3. 2H2 + O2 → 2H2O How are reactants and products related?
Reactants are the materials you start a reaction with
and the products are the materials you end with.

4. 2H2 + O2 → 2H2O How is a subscript different from a coefficient?
A subscript is lower and smaller and follows an element’s
symbol. It represents the number of atoms of that element
in a molecule. (O2)
A coefficient is the number in front of a chemical formula
and it shows the number of molecules. (2 H2O)

5. 2H2 + O2 → 2H2O How is a chemical equation different from
This is a formula
How is a chemical equation different from
a chemical formula?
A chemical equation is a short, easy way to show
a chemical reaction using symbols.
A chemical formula is a combination of symbols
that represent the elements in a compound.
This entire thing is an equation

6. Analyze the following:
N2 + 3H2  2NH3
What are the reactants? Product(s)
How many atoms of N are present in the reactants? Products?
How many atoms of H are present in the reactants? Products?

7. Analyze the following 2CuO + C  2Cu + CO2
What are the reactants? Product(s)
How many atoms of each element are present in the reactants? Products?

8. Analyze the following H2 + Cl2  HCl
What are the reactants? Product(s)?
How many atoms of H are present in the reactants? Products?
How many atoms of Cl are present in the reactants? Products?
Do you see a difference between the analysis of this equation and the previous two?

9. Balancing Chemical Equations
H2 + O2  H2O

10. Balancing Chemical Equations
Law of Conservation of Matter:
Matter cannot be created or destroyed, it can only be transformed
When writing chemical equations, the law of conservation of mass is observed:
This means that the numbers of atoms of each element must be the same on each side of the equation
In equation 1 and 2, the numbers of each type of element were the same in reactants and products.
In equation 3 they aren’t.

11. Balancing Chemical Equations
We balance equations to account for and accommodate the Law of Conservation of Matter. We’ve learned in the previous unit that the CHEMICAL FORMULA is determined by electron configuration and obeys the Law of Conservation of Charge. Because of that, we can’t just change subscripts to show Law of Conservation of Matter. We must use coefficients.

12. Balancing Chemical Equations
Example A
N2 + H2  NH3
Example B
NaCl + F2  NaF + Cl2

13. Balancing Chemical Equations
Practice:
P O2  P2O5
Na H2O  NaOH H2
HCl + CaCO3  CaCl H2O CO2

14. Steps for Balancing Chemical Equations
“Take Inventory” Count the numbers of atoms of each element in each side of the equation
Choose which side to start
Adjust coefficient of molecule and adjust the inventory
Repeat until the numbers of each type of atoms on each side matches
NEVER EVER EVER EVER CHANGE A SUBSCRIPT
NEVER EVER EVER INSERT A COEFFICIENT IN THE MIDDLE OF A FORMULA
PRACTICE, PRACTICE, PRACTICE

15. Classifying Chemical Reactions
1. Synthesis 2 or more substances combine
2SO2 + O2 + 2H2O  2H2SO4
(A B + C  ABC)
2. Decomposition breaking down compounds
2H2O2  2H2O + O2
(AB  A B)
3. Single Replacement single - 1 element replaces another
in a compound
2CuO + C  2Cu + CO2
(AB C  A + BC)
4.Double Replacement double - 2 elements in different
compounds trade places
RbBr + AgCl  AgBr + RbCl
(AB CD  CB AD)
5. Combustion hydrocarbon (fuel) plus oxygen yields carbon dioxide plus water

16. Balance and classify the following chemical reactions
____ Na +____ I2  ____ NaI
____ KClO3  ____ KCl + ____ O2
____Na + ____ HCl  ____ NaCl + ___ H2
____ K3PO4 + ____ HCl  ____ KCl + ____ H3PO4
____ C3H8 + ____ O2  ____ CO2 + ____ H2O