CHEMICAL EQUATIONS
Chemical equations are a representations of a
chemical reaction in terms of the symbols of the
elements and compounds involved in the
reaction.
Chemical equations are separated into two parts,
the reactants and the products.
Given the general equation for a reaction:
A and B are the reactants which are consumed
in the reaction.
C and D are the products which are formed by
the reaction.
BALANCING CHEMICAL EQUATIONS
Chemical equations are balanced when they
have the same number of each element on both
sides of the equation.
Which of the following equations are balanced?
Î
2H2O 6 2H2 + O2
Ï
CaO + CO2 6 CaCO3
Ð
Na + CuCl2 6 NaCl + Cu
ÑFeBr3 + 3KOH 6 Fe(OH)3 + 3KBr
Ò
F2 + LiI 6 LiF + I2
The formula of compounds can never be
changed once they are written correctly in a
chemical reaction
The number of particles in a chemical reaction
can only be changed by adding a coefficient
before the symbol for the substance.
When balancing equations, always start at the
most complex substance or the one with the
most particles
H2O 6 H2 + O2
H2O
2-H
1-O
6
H2
2-H
+
O2
2-O
Hg + O2 6 HgO
Hg
1-Hg
+
O2
2-O
6
HgO
1-Hg
1-O
Na + CuCl2 6 NaCl + Cu
Na
1-Na
+
CuCl2
1-Cu
2-Cl
6 NaCl +
1-Na
1-Cl
Cu
1-Cu
FeBr3 + NaOH 6
FeBr3
1-Fe
3-Br
Fe(OH)3 + NaBr
+ NaOH 6 Fe(OH)3 + NaBr
1-Na
1-Fe
1-Na
1-OH
3-OH
1-Br
F2 + LiI 6 LiF + I2
F2
2-F
+
LiI
1-Li
1-I
6
LiF
1-Li
1-F
+
I2
2-I
ZnCl2 + (NH4)3PO4 6 Zn3(PO4)2 + NH4Cl
ZnCl2 + (NH4)3PO4 6 Zn3(PO4)2 + NH4Cl
1-Zn
3-NH4
3-Zn
1-NH4
2-Cl
1-PO4
2-PO4
1-Cl
AgNO3 + K2CO3 6 Ag2CO3 + KNO3
AgNO3 + K2CO3 6 Ag2CO3 + KNO3
1-Ag
2-K
2-Ag
1-K
1-CO3
1-CO3
1-NO3
1-NO3
Ca(HCO3)2 6 CaO + CO2 + H2O
Ca(HCO3)2 6 CaO
1-Ca
1-Ca
2-H
1-O
2-C
6-O
+ CO2 + H2O
1-C
2-H
2-O
1-O
When an element is found in more than one compound, balance it
last.
NH3 + O2 6 N2 + H2O
NH3
1-N
3-H
+
O2
2-O
6
N2
2-N
+
H2O
2-H
1-O
If you are unable to balance an equation at first, try doubling the
number of particles contained in the most complex substance and
balance the equation using twice the number of particles.
CH4 + O2 6 CO2 + H2O
CH4
1-C
4-H
+
O2
2-O
6
CO2
1-C
2-O
+
Complete combustion of a hydrocarbon (carbon - hydrogen
compound) always produces carbon dioxide and water as the
products
H2O
2-H
1-O
C3H8 + O2 6 CO2 + H2O
C3H8
3-C
8-H
+
O2
2-O
6
CO2
1-C
2-O
+
H2O
2-H
1-O
C2H6 + O2 6 CO2 + H2O
C2H6
2-C
6-H
+
O2
2-O
6
CO2
1-C
2-O
+
H2O
2-H
1-O
C2H2 + O2 6
C2H2
2-C
2-H
+
O2
2-O
6
CO2
1-C
2-O
+
H2O
2-H
1-O
CH3OH + O2 6
CH3OH +
1-C
4-H
1-O
O2
2-O
6
CO2
1-C
2-O
+
H2O
2-H
1-O
TYPES OF CHEMICAL EQUATIONS
Î Word equation
In word equations, the names of the reactants and products are
written out. The following example is a word equation:
carbon + oxygen 6 carbon dioxide
Ï Formula equations
Formula equations consist of formulas substituted for the names
in the word equation. The reaction above becomes
C + O2 6 CO2
Ð Ionic equations
In ionic equations, all water soluble compounds in an aqueous
solution are separated into ions.
2NaI(aq) + Pb(NO3)2(aq) 6
2NaNO3(aq) + PbI2(s)
2Na+(aq) + 2I-(aq) + Pb2+(aq) + 2NO3-(aq) 6
+
2Na (aq) + 2NO3 (aq) + PbI2(s)
Spectator ions - Spectator ions do not participate in the chemical
reaction. That is, they are identical on both sides of the equation.
Ñ Net ionic equations
The net ionic equation contains all of the particles in the ionic
equation less any spectator ions.
2Na (aq) + 2I (aq) + Pb (aq) + 2NO3 (aq) 6
+
2Na (aq) + 2NO3 (aq) + PbI2(s)
+
-
2+
Pb2+(aq) + 2I-(aq) 6 PbI2(s)
-
TYPES OF CHEMICAL REACTIONS
Î Synthesis or Combination Reactions
A+B6C
Ï Decomposition Reactions
C6A+B
Ð Single Replacement Reactions
M + BC 6 MC + B
N + BC 6 BN + C
Ñ Double Replacement Reactions
AB + CD 6 AD + CB
Ò Combustion Reactions
CxHy + O2 6 xCO2 + y/2H2O
Synthesis or Combination Reactions
C In synthesis or combination reactions, two or
more substances combine together to form a
single product.
C The general form is
A+B6C
C The products must contain only those
elements found in the reactants.
C Metal oxide + water 6 metal hydroxide
C Metal oxide + carbon dioxide 6
metal carbonate
C Metal oxide + sulfur dioxide 6 Metal sulfite
Predict the names of the products in each of the
following reactions:
Zinc + oxygen 6
Sodium + sulfur 6
Calcium oxide + water 6
Sodium oxide + carbon dioxide 6
Write a balanced formula equation for the
reaction below:
Zinc + Oxygen 6 Zinc Oxide
Zn + O2 6 ZnO
Zn
1-Zn
+
O2
2-O
6
ZnO
1-Zn
1-O
Sodium + Sulfur 6 Sodium Sulfide
Na + S 6 Na2S
Na
1-Na
+
S
1-S
6
Na2S
2-Na
1-S
Calcium Oxide + Water 6 Calcium Hydroxide
CaO + H2O 6 Ca(OH)2
CaO
1-Ca
1-O
+
H2O 6 Ca(OH)2
2-H
1-Ca
1-O
2-O
2-H
Sodium Oxide + Carbon Dioxide 6
Sodium Carbonate
Na2O + CO2 6 Na2CO3
Na2O
2-Na
1-O
+
CO2
1-C
2-O
6 Na2CO3
2-Na
1-C
3-O
Complete the word equation, give the correct formulas, and write
the balanced formula equation for the following reaction:
Aluminum + Oxygen 6
Aluminum + Oxygen6 Aluminum Oxide
Al + O2 6 Al2O3
Al
1-Al
+
O2
2-O
6
Al2O3
2-Al
3-O
Complete the word equation, give the correct formulas, and write
the balanced formula equation for the following reaction:
Potassium + Chlorine 6
Potassium + Chlorine 6 Potassium Chloride
K + Cl2 6 KCl
K
1-K
+
Cl2
2-Cl
6
KCl
1-K
1-Cl
Complete the word equation, give the correct formulas, and write
the balanced formula equation for the following reaction:
Gallium Oxide + Water 6
Gallium Oxide + Water 6 Gallium Hydroxide
Ga2O3
2-Ga
3-O
+
H2O
2-H
1-O
6
Ga(OH)3
1-Ga
3-O
3-H
DECOMPOSITION REACTIONS
C Substances break down by means of
decomposition reactions
C The general form of a decomposition reaction
is
C6A+B
C Decomposition reaction are the opposite of
combination or synthesis reactions
C Heating a metal carbonate always yields the
metal oxide and carbon dioxide.
MCO3 6 MO + CO2
C Heating a metal hydroxide gives the metal
oxide and water
MOH 6 MO + H2O
C Heating a metal sulfite produces a metal oxide
and sulfur dioxide
MSO3 6 MO + SO2
C Heating a metal bicarbonate gives the metal
oxide, carbon dioxide, and water.
MHCO3 6 MO + H2O + CO2
C Heating a metal chlorate gives the metal
chloride plus oxygen.
MClO3 6 MCl + O2
C Electrolysis of a molten salt (ionic compound)
separates the substance into its elements.
MN 6 M + N
Predict the products in each of the following
reactions:
â Calcium Carbonate
ã Lithium Chlorate
ä Sodium Bicarbonate
å Potassium Chloride
æ Aluminum Hydroxide
ã Lithium Chlorate
Lithium Chlorate 6 Lithium Chloride + Oxygen
LiClO3
1-Li
1-Cl
3-O
6
LiCl
1-Li
1-Cl
+
O2
2-O
â Calcium Carbonate
Calcium Carbonate 6
Calcium Oxide + Carbon Dioxide
CaCO3
1-Ca
1-C
3-O
6
CaO
1-Ca
1-O
+
CO2
1-C
2-O
ä Sodium Bicarbonate
Sodium Bicarbonate 6 Sodium Oxide + Carbon Dioxide + Water
NaHCO3 6 Na2O
1-Na
2-Na
1-H
1-O
1-C
3-O
+
CO2
1-C
2-O
+
H2O
2-H
1-O
å Potassium Chloride
Potassium Chloride 6 Potassium + Chlorine
KCl
1-K
1-Cl
6
K
1-K
+
Cl2
2-Cl
æ Aluminum Hydroxide
Aluminum Hydroxide 6
Aluminum Oxide + Water
Al(OH)3 6
1-Al
3-O
3-H
Al2O3 + H2O
2-Al
2-H
3-O
1-O
Complete the word equation, give the correct formulas, and write
the balanced formula equation for the following reaction:
Sodium Hydroxide
Sodium Hydroxide 6 Sodium + Oxygen + Hydrogen
NaOH 6 Na
1-Na
1-Na
1-O
1-H
+
O2
2-O
+
H2
2-H
Complete the word equation, give the correct formulas, and write
the balanced formula equation for the following reaction:
Iron (III)
Carbonate
Iron (III) Carbonate 6 Iron (III) Oxide + Carbon Dioxide
Fe2(CO3)3
2-Fe
3-C
9-O
6
Fe2O3
2-Fe
3-O
+
CO2
1-C
2-O
Complete the word equation, give the correct formulas, and write
the balanced formula equation for the following reaction:
Chromium (III) Chlorate
Chromium (III) Chlorate 6 Chromium (III) Chloride + Oxygen
Cr(ClO3)3
1-Cr
3-Cl
9-O
6
CrCl3
1-Cr
3-Cl
+
O2
2-O
Complete the word equation, give the correct formulas, and write
the balanced formula equation for the following reaction: