Chemical Equations and
Reactions
Balancing Chemical Equations
Balancing Equations
1.
2.
3.
4.
5.
ONLY add/change Coefficients- NEVER
subscripts!!!
balance polyatomic ions first
(sometimes they can stay grouped)
Then balance atoms that appear only once
balance H and O last
simplify if you can
1.
6.
You must be able to simplify ALL the
coefficients
Check at end! Are both sides equal?
Balancing Equations
There are multiple methods of balancing.
Choose the method that works best for YOU.
1. Free Hand
2. Tic-tac-toe chart
3. Table form (this is the one I prefer)
Example 1
 Description:
Zinc metal is added to hydrochloric acid to
create zinc chloride and hydrogen gas.
 Word Equation:
zinc + hydrochloric acid 
zinc chloride + hydrogen
 Formula Equation:
Zn (s) + HCl(aq)  ZnCl2(aq) + H2(g)
 Balanced Formula Equation
1 Zn (s) + 2 HCl(aq)  1 ZnCl2(aq) + 1 H2(g)
Example 2
 Solid
calcium metal reacts with water to
form aqueous calcium hydroxide and
hydrogen gas.
 calcium + water 
calcium hydroxide + hydrogen
 Ca(s) + H2O(l)  Ca(OH)2(aq) + H2(g)
 1 Ca(s) + 2 H2O(l)  1 Ca(OH)2(aq) + 1 H2(g)
Example 3
 Hydrogen
peroxide in an aqueous
solution decomposes to produce
oxygen and water
 hydrogen peroxide  oxygen + water
 H2O2(aq)  O2(g) + H2O(l)
 2 H2O2(aq)  1 O2(g) + 2 H2O(l)
Example 4
 Solid
copper metal reacts with aqueous
silver nitrate to produce solid silver metal
and aqueous copper (II) nitrate
 copper + silver nitrate 
silver + copper (II) nitrate

Cu(s) + AgNO3(aq)  Ag(s) + Cu(NO3)2(aq)

1 Cu(s) + 2 AgNO3(aq)  2 Ag(s) + 1 Cu(NO3)2(aq)
Example 5
 solid
zinc metal reacts with aqueous
copper (II) sulfate to produce solid copper
metal and aqueous zinc sulfate
 zinc
+ copper (II) sulfate 
copper + zinc sulfate
 Zn(s) + CuSO4(aq)  Cu(s) + ZnSO4(aq)
 ALREADY BALANCED