1. Writing and Balancing Equations
What do we know already?

2. Word Equation Potassium metal + oxygen gas  potassium oxide Yields
Produces
In math, this means ‘equals’
Reactants
Products

3. Skeleton (Unbalanced) Equation
A skeleton equation shows the formulas of the elements/compounds – it is unbalanced
Shows atoms, but not quantities of atoms
K(s) + O2 (g)  K2O(s)
(The states of matter may or may not be shown... That’s OK)

4. Counting Atoms in a Compound
To correctly balance an equation, you must make sure you know how many of each atom are on each side of the arrow
Try these:
Br2
2FeBr3
4K3PO4
Sn3(PO4)4
3Sn3(NO2)4

5. So what’s wrong with a Skeleton??
K(s) + O2 (g)  K2O(s)
Remember the Conservation Law?
Atoms cannot be created or destroyed in a chemical reaction!
The atoms in the reactants must also be in the products
(even though they have been rearranged)

6. How do we balance an equation?
You must count the number and type of atoms on the reactant side versus the product side
Do it all in your head... Ick, sounds too confusing!

7. Counting Atoms by Using a T-Table
Let’s use the overhead for these ones...
Reactants
Products

8. Tips for Balancing Equations:
Trial and error will work, but can be very slow!
Polyatomic ions can often be balanced as a whole group (as long as the group is on BOTH sides of the equation)
Sn(NO2)4 + K3PO4  KNO2 + Sn3 (PO4)4
Only write in co-efficients
(the #’s IN FRONT of the elements)
NEVER mess with the subscripts
Balance the H’s second last
Balance the O’s last
Always double-check when you think you’re finished!