Balancing Equations
Potassium Iodide and Lead Nitrate
are mixed to form a precipitate
(solid). After the reaction the mass
of the flask will
1.
2.
3.
Increase
Decrease
Stay the same
33%
1
33%
2
33%
3
Chemical Reactions
Shown by chemical equations
4
Cu (s)
coefficients
+ 1
O2 (g) 
2 Cu2O (s)
Symbols


s
l
g
aq
yields, reacts to form
reversible reaction
heat is added
solid
liquid
gas
aqueous (dissolved in
water)
Sides?
Reactant(s)
Product(s)
2Fe + O2  2FeO
“Rust”
Why Balance?


To show that the law of conservation of
mass is satisfied
To know the proportions the elements and
compounds react in
Balancing Equations using
Atom Inventory
Zn +2 HBr  ZnBr2 + H2
Balanced!!
1
Zn
1
2 1
H
2
2 1
Br
2
Is everthing
balanced?
Leave Polyatomic ions together
2 AgNO3 + Na2S  Ag2S + 2 NaNO3
Balanced!!
2 1
Ag
2
1
S
1
2
Na
12
NO3
12
2 1
Is everthing
balanced?
Never change subscripts
Al2(SO4)3 + 6HCl  3H2SO4 +2 AlCl3
2
Al
12
Balanced!!
3
SO4
13
6 1
H
2 6
6 1
Cl
36
Is everthing
balanced?
Websites



www.funbasedlearning.com (open with Internet
Explorer)
http://education.jlab.org/elementbalancing/inde
x.html
http://science.widener.edu/svb/tutorial/rxnbala
ncingcsn7.html