1. Balancing Equations

2. Chemical Reactions   All chemical reactions can be represented by an equation.   The arrow means that a reaction has taken place.   Your starting materials or reactants must be written to the left of the arrow.   Your new substances or products must be written to the right of the arrow

3. Reactants Products

4. You must start with the correct formulas Count the atoms of each element before the reaction and after the reaction. If you have the same number of atoms of each element before and after the reaction then your equation is balanced.

5. NaOH + HCl NaCl + H 2 O Before the reaction: 1 atom of sodium 1 atom of oxygen 2 atoms of hydrogen 1 atom of chlorine After the reaction: 1 atom of sodium 1 atom of oxygen 2 atoms of hydrogen 1 atom of chlorine This equation is BALANCED

6. Mg + HCl MgCl 2 + H 2 Before the reaction: 1 atom of magnesium 1 atom of hydrogen 1 atom of chlorine After the reaction: 1 Atom of magnesium 2 atoms of hydrogen 2 atoms of chlorine This equation is unbalanced

7. When balancing an equation you must not change any formulas. You can only add the whole formula again Mg + HCl MgCl 2 + H 2 HCl Before the reaction: 1 atom of magnesium 2 atoms of hydrogen 2 atoms of chlorine After the reaction: 1 Atom of magnesium 2 atoms of hydrogen 2 atoms of chlorine

8. The equation is now balanced Mg + 2HCl MgCl 2 + H 2

9. Now you try these: 1. Ca + O 2 CaO 2. Na + Cl 2 NaCl 3. H 2 + O 2 H 2 O