1. Balancing Equations
Just repeat:
“I know I can, I know I can!”

2. Balancing equations
 Dueto the conservation of matter,
equations MUST be balanced!
 Atoms cannot be created or destroyed!
 Thus, the atoms in the products must
equal the total atoms in the reactants
REMEMBER: The atoms are only being
rearranged!

3. Coefficients vs. Subscripts
 Subscripts tell us how many atoms
there are in the molecule.
O2
This tells us that there are 2 Oxygen atoms
bonded to each other: O=O
 Coefficients tell us how many
molecules there are.
2O2
This tells us that there are 2 molecules of
O2 O=O and O=O

4. How to balance an equation
 Writeout the equation with the
reactants and products formulas
MgO + HBr ---> MgBr2 + H2O
Magnesium oxide and Hydrogen Bromide
becomes Magnesium Bromide and Water.

5. How to balance an equation
 Countthe Atoms of each element on
both sides of the equation.
MgO + HBr ---> MgBr2 + H2O
1 Mg 1 Mg
1O 1O
1H 2H
1 Br 2 Br

6. How to balance an equation
 Usecoefficients to balance the
equation
MgO + HBr ---> MgBr2 + H2O
We need a total of two hydrogen and
bromine on the reactants side in order
to balance this equation.

7. How to balance an equation
 Finally…. Our balanced equation
MgO + 2HBr ---> MgBr2 + H2O
Double check your work, by counting again:
1 Mg 1 Mg
1O 1O
2H 2H
2 Br 2 Br

8. Try one on your own!
H + O  H 2O
H- 1 H- 2
O- 1 O- 1
2H + O  H2O

9. Let’s do another, for fun!!
Fe + HCl ---> FeCl2 +H2
1 Fe 1 Fe
1H 2H
1 Cl 2 Cl
Fe + 2HCl ---> FeCl2 +H2

10. Let’s try a couple more…
N2 + O2 ---> N2O5
2N 2N
2O 5O
We need to balance out the Oxygen first,
then the Nitrogen. This gives us…
2N2 + 5O2 ---> 2N2O5
4N 4N
10 O 10 O

11. One More…
C2H4 + O2 ---> CO2 + H2O
2C 1C
4H 2H
2O 3O
C2H4 + 3O2 ---> 2CO2 + 2H2O