1. Chemical equations

2. What are chemical equations?
A short, easy way to show a chemical reaction.
Chemical equations use chemical formulas and other symbols instead of words to summarize a reaction.

3. Parts of a Chemical Equation
REACTANTS are on the LEFT and PRODUCTS are on the RIGHT

4. Count the atoms in the Chemical Equation
Count the number of atoms for each element on both sides
Ca = ___ C = ___ O = ___ Ca = ___ C = ___ O = ___

5. Count the atoms in the Chemical Equation
Count the number of atoms for each element on both sides
Ca = _1_ C = _1_ O = _3_ Ca = _1_ C = _1_ O = _3_

6. Count the atoms in the Chemical Equation
Ca = _1_ C = _1_ O = _3_ Ca = _1_ C = _1_ O = _3_
Is the chemical equation balanced?
YES, there are the same number of atoms for each element on both sides.

7. Why does a chemical equation need to be balanced?
The Law of Conservation of Mass states that in a chemical reaction, the total mass of the reactants must equal the total mass of the products.
*Remember… Matter cannot be created nor destroyed!

8. Is this equation balanced?
Let’s count the atoms to find out…
H O2  H2O
H = H =
O = O =

9. Is this equation balanced?
Let’s count the atoms to find out…
H O2  H2O
H = H = 2
O = O = 1
NO!

10. How can we balance the equation?
The only thing we can do to balance a chemical equation is to ADD COEFFICIENTS.
Coefficients increase the
number of atoms.
They multiply through the
symbol/formula.
*You CANNOT change
the subscripts!
H = 4 H = 4
O = 2 O = 2

11. We need to add coefficients to balance the equation.
2 H2 + O2  2 H2O
H2 + O2  H2O
This equation is NOT balanced! There are more oxygen atoms on the left.

12. Practice example This equation is not balanced… Count the atoms.
__ Na __ Cl2  __ NaCl
Na = Na = 1
Cl = Cl = 1

13. Balancing chemical equations
Add Coefficients…
__ Na __ Cl2  2 (NaCl)
Na = Na = 2
Cl = Cl = 2

14. Balancing chemical equations
Add Coefficients…
2 (Na) __ Cl2  2 (NaCl)
Na = Na = 2
Cl = Cl = 2
Balanced!