Balancing Equations
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
Reactants
Products
•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.
NaOH + HCl
NaCl + H2O
Before the reaction:
After the reaction:
1 atom of sodium
1 atom of sodium
1 atom of oxygen
1 atom of oxygen
2 atoms of hydrogen
2 atoms of hydrogen
1 atom of chlorine
1 atom of chlorine
This equation is BALANCED
Mg +
HCl
MgCl2
+ H2
Before the reaction:
After the reaction:
1 atom of magnesium
1 Atom of magnesium
1 atom of hydrogen
2 atoms of hydrogen
1 atom of chlorine
2 atoms of chlorine
This equation is unbalanced
•When balancing an equation you must not change any
formulas.
•You can only add the whole formula again
Mg + HCl
MgCl2
+ H2
HCl
Before the reaction:
After the reaction:
1 atom of magnesium
1 Atom of magnesium
2 atoms of hydrogen
2 atoms of hydrogen
2 atoms of chlorine
2 atoms of chlorine
The equation is now balanced
Mg + 2HCl
MgCl2 + H2
Now you try these:
1. Ca + O2
CaO
2. Na + Cl2
NaCl
3. H2 + O2
H2O