1. Balancing Equations

2. CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g)
Chemical Equations
Chemical Equations are concise representations of chemical reactions.
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g)

3. Anatomy of a Chemical Equation
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g)
Reactants appear on the left side of the equation.

4. Anatomy of a Chemical Equation
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g)
Products appear on the right side of the equation.

5. Anatomy of a Chemical Equation
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g)
The states of the reactants and products are written in parentheses to the right of each compound.

6. Anatomy of a Chemical Equation
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g)
Coefficients are the numbers which appear before a compound

7. Anatomy of a Chemical Equation
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g)
Subscripts are the numbers which appear in a compound

8. Subscripts and Coefficients
Subscripts tell the number of atoms of each element in a molecule
Coefficients tell the number of molecules
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g)
The coefficient 2 tells us that we have two total water molecules. Coefficients tell the number of molecules.
The subscript 2 informs us that this compound consists of two hydrogen atoms bonded to one oxygen atom. Subscripts tell us the number of atoms in a compound.

9. Subscripts and Coefficients
To know how many total atoms there are of a specific element we multiply the subscript by the coefficient.
For example: Multiply the subscript 2 by the coefficient 2 to get a total of 4 hydrogen atoms.
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g)
To know how many oxygen atoms we have on the product side we would have to add the oxygen in carbon dioxide to the oxygen in water: 2 O + 1 O = 3 O

10. Balancing Equations

11. Balancing Equations Law of Conservation of Matter:
In a chemical reaction, matter can be neither created nor destroyed.

12. Balancing Equations In other words:
The number of atoms of each type of element must be the same on each side of the equation.

13. Balancing Equations H2 + O2 H2O
The subscripts on Hydrogen and Oxygen cannot be changed.
The subscripts on water cannot be changed.
NEVER CHANGE SUBSCRIPTS!

14. Balancing Equations H2 + O2 H2O
If the subscripts cannot be altered, how can the atoms be made equal?
Adjust the number of atoms by changing the coefficients.

15. Practice H2 + O2 H2O Count the atoms on each side. Reactant side:
2 atoms H
2 atoms O
—Product side:
2 atoms H
1 atom O

16. Practice H2 + O2 2H2O Count the atoms on each side. Reactant side:
2 atoms H
2 atoms O
—Product side:
4 atoms H
2 atoms O
Hydrogen is no longer balanced. We must balance the hydrogen!

17. Practice 2H2 + O2 2H2O Count the atoms on each side. Reactant side:
4 atoms H
2 atoms O
—Product side:
4 atoms H
2 atoms O

18. Practice N2 + H2 NH3 Count the atoms on each side. Reactant side:
2 atoms N
2 atoms H
—Product side:
1 atom N
3 atoms H

19. Practice N2 + H2 2NH3 Count the atoms on each side. Reactant side:
2 atoms N
2 atoms H
—Product side:
2 atoms N
6 atoms H

20. Practice N2 + 3H2 2NH3 Count the atoms on each side. Reactant side:
2 atoms N
6 atoms H
—Product side:
2 atoms N
6 atoms H