1. CHEMICAL FORMULAS & EQUATIONS

2. CHEMICAL FORMULA Everyone knows at least one chemical formula H2O
This represents the presence of 2 Hydrogens and one oxygen in every molecule of water
Any number below the line applies to the element in front of it

3. CHEMICAL FORMULAS & RATIOS
Molecules have very specific numbers of atoms present.
If I change water to H2O2 it becomes peroxide
Salts are represented by the simplest ratio of elements, i.e table salt, NaCl or Magnesium Chloride, MgCl2

4. CONSERVATION OF MASS
Mass can be neither created nor destroyed
In a chemical reaction reactants (left side of the equation)are disassembled and rearranged in to products (right side of the equation)
Mass is conserved

5. CHEMICAL EQUATIONS A chemical equation is like a mathematical equation
C2H6 + O2 →CO2 + H2O
REACTANTS PRODUCTS
The number of atoms on the reactant side must equal the number of atoms on the product side.

6. BALANCING A CHEMICAL EQUATION
C2H6 + O2 →CO2 + H2O
2 C C
6 H H
2 O O
We can’t change the number below the line so what can we do?

7. BALANCING A CHEMICAL EQUATION
When you add a number in front of a molecule it applies to the whole molecule.
C2H6 + 31/2 O2 → 2 CO2 + 3 H2O
Whole numbers are preferable but in VCE chemistry half numbers are allowable
2 C2H O2 → 4 CO H2O

8. FINAL STEP
To complete your chemical equation add states of matter
2C2H6 (g)+ 7O2 (g)→ 4CO2 (g) + 6H2O (g)
(g) = gas (aq) = aqueous (l) = liquid (s) = solid

9. Can you balance these equations?
Mg(s) + O2(g) → MgO(s)
H2SO4(aq) + NaOH(aq) → Na2SO4(aq) + H20(l)