Balancing Chemical Equations Notes
1.
Counting Atoms
a. Given the mock chemical equation below (not balanced), how can we determine the number of atoms on the reactant side and
the product side?
2 Al (s) + 3 CuCl3 (g)  2 AlCl3 (g) + 3 Cu (s)
b.
c.
Step #1: ___________ the ___________ and ___________ sides of the ___________ equation
Step #2: ___________ the ___________ of ___________ on the ___________ and ___________ side doing the following
i. For each ___________, ___________ the ___________ in ___________ of the ___________ or ___________ by its
___________
ii. If there is no ___________ or ___________, assume it equals “__”
iii. Ignore the ________of ___________ for each ___________ or ___________, it is ___________
2 Al (s) + 3 CuCl3 (g)  2 AlCl3 (g) + 3 Cu (s)
Al
Reactant Side
CuCl3
Product Side
Total
AlCl3
Cu
Total
Aluminum
Copper (III)
Chlorine
d.
Step #3: If you have an ___________ or ___________ within ___________ that are ___________ on ___________ sides of the
___________
i. ___________ the ___________ of the ___________ in the ___________ by the ___________ outside the ___________.
ii. Then ___________ your ___________ by the ___________ (if applicable) to determine the number of ___________
2 (NH4)2Cr2O7 (s)  2 Cr2O3 (s) + 8 H2O (g) + 2 N2 (g)
Reactant Side
(NH4)2Cr2O7
Total
Cr2O3
Product Side
H2O
N2
Total
Nitrogen
Hydrogen
Chromium
Oxygen
e.
Counting Atoms Classwork: Given the following chemical equations, count how many atoms are on the reactant and product
sides
Pb(NO3)2 (aq) + K2CO3 (aq)  PbCO3 (s) + 2 KNO3
Br2 (l) + 2 NaI (aq)  2 NaBr(aq) + 3 I2(s)
AgNO3 (aq) + KBr (aq)  3 AgBr (s) + 2 KNO3 (aq)
Ca(OH)2 (aq) + HCl (aq)  CaCl2 (aq) + H2O (l)
2.
Balancing Chemical Equations
a. Assume we have the following unbalanced equation:
H2 (g)
b.
+
O2 (g)

H2O (g)
The ___________step is to ___________the ___________of ___________on the ___________and ___________sides!
Reactant Side
O2
H2
Product Side
H2O
Total
Total
Hydrogen
Oxygen
c.
Step #2: After ___________the ___________, pick an ___________that ___________easy to ___________
i. Place a ___________on the ___________side (___________or ___________) to ___________the ___________count
___________on the ___________and ___________sides
ii. Then ___________all your ___________based on the ___________you’ve ___________
iii. In the example, ___________is the easiest to ___________first (as the ___________side has ___________times more
than the ___________side)
H2 (g)
+
O2 (g)

Reactant Side
O2
H2
H2O (g)
Product Side
H2O
Total
Total
Hydrogen
Oxygen
d.
Step #3: ___________this ___________until all the ___________are ___________on the ___________and ___________sides!
H2 (g)
+
H2
O2 (g)
Reactant Side
O2

H2O (g)
Product Side
H2O
Total
Total
Hydrogen
Oxygen
e.
Assume we have the following unbalanced equation:
f.
The first step is to ___________the ___________of ___________on the ___________and ___________sides!
Fe3O4 + H2 
Fe3O4
Reactant Side
H2
Fe + H2O
Total
Fe
Product Side
H2O
Total
Iron
Oxygen
Hydrogen
g.
Step #2: Start ___________by adding ___________. Pick an “___________” element to ___________. In this case,
___________is ___________as you want to save the “___________” element (___________on the product side) for last!
Fe3O4 + H2 
Fe3O4
Reactant Side
H2
Fe + H2O
Total
Fe
Product Side
H2O
Total
Fe
Product Side
H2O
Total
Iron
Oxygen
Hydrogen
h.
Step #3: Keep going until the equation is balanced!
Fe3O4 + H2 
Fe3O4
Iron
Oxygen
Hydrogen
Reactant Side
H2
Fe + H2O
Total