1. BALANCING CHEMICAL EQUATIONS
Chapter 6.5
DAY 1 & 2

2. Word equations or formula (skeleton) equations need to be balanced.
The number of atoms of one element on the reactant side of an equation must equal the number of atoms of that same element on the product side of an equation.

3. LAW OF CONSERVATION OF MASS
This law states: the total mass of atoms must be the same on both sides of an equation.
This means that the mass of the reactants equals the mass of the products.
In other words, atoms can be neither created or destroyed in a chemical change.

4. How to count atoms review
Using Black line 6.5a, we will review counting atoms before we learn the skill of balancing equations.

5. 1) The symbol of an element represents one atom of that element Example: Ca = 1 atom 2) A subscript is a number written at the lower right corner after the symbol of an element. If there is more than one atom of the element in the molecule, then a subscript is used to indicate the number of atoms. Example: N2 = 2 atoms

6. 3) A subscript outside a bracket multiplies all the elements inside the brackets.
Example: Ba3(PO4)2
Barium – 3 atoms
Phosphorus – 2 atoms
Oxygen – 8 atoms
4a) A coefficient is a number written in front of a chemical symbol and indicates the number of atoms of that element.
Example: 3C = 3 carbons

7. 4b) A coefficient is a number written in front of a chemical formula and indicates the number of molecules of that compound.
2H2O = Hydrogen 2 x 2 = 4 atoms,
Oxygen 1 x 2 = 2 atoms
NOTE: A coefficient multiplies the number of atoms of each element in the formula.
4Cu(NO3)2 =
Copper 1 x 4 = 4 atoms,
Nitrogen 1 x 2 x 4 = 8 atoms,
Oxygen 3 x 2 x 4 = 24 atoms

8. LET’S BALANCE EQUATIONS
STEP 1 – Write the formula equation of the reaction. Example: CH4 + O2 CO2 + H2O

9. STEP 2 – Count the number of atoms of each type on the reactants side and on the products side
reactants products
O – O - 3
C – C - 1
H – H – 2

10. Step 3 Multiply each of the formulas by an appropriate coefficient to balance the numbers of atoms. CH4 + 2 O2 CO2 + 2 H2O Step 4 Count atoms on each side to verify. reactants products O – 4 O - 4 C – 1 C - 1 H – 4 H – 4

11. hydrogen and oxygen produce water
H2 + O H2O
PRACTICE

12. Aluminum and Oxygen produce Aluminum Oxide
Al + O Al2O3
Practice

13. Ethylene and Oxygen produces carbon dioxide and water
C2H4 + O2 CO2 + H20
Practice

14. Practice Carbon dioxide and hydrogen produces Methane and water
CO2 + H CH H20
Practice

15. PAGE 229 # 2, 3ade Practice worksheet BLM 6.5c Assignment
Class Work