SCH 3U
Chemical Reactions
Name: _________________________
Types of Chemical Reactions
A) DECOMPOSTION
AB  A + B
During a decomposition reaction, one compound splits into two or more pieces. These smaller pieces can be elements or
simpler compounds.
Examples:
magnesium chloride magnesium + chlorine
calcium carbonate  calcium oxide + oxygen
potassium chlorate  potassium chloride + oxygen
iron(III) hydroxide  iron (III) oxide + water
carbonic acid  carbon dioxide + water
2 H2O  2 H2 + O2
Na2CO3  Na2O + CO2
Ba(ClO3)2  BaCl2 + 3 O2
Cu(OH)2  CuO + H2O
2 H3PO4  P2O5 + 3 H2O
The following rules will help when determining the products of a decomposition reaction.
1.
2.
3.
4.
5.
All binary compounds will break down into their elements.
All carbonates break down to the metal oxide and carbon dioxide gas.
All chlorates break down to the metal chloride and oxygen gas.
Metal hydroxides break down to the metal oxide and water.
Oxy acids break down to the non-metal oxide (with the non-metal having the same valence) and water.
Practice Problems: Provide a completed word and full balanced chemical equation for each reaction.
a) nickel (II) chloride  nickel + chlorine
g) Cs2CO3  2 CsO + CO2
2 NiCl3  2 Ni + 3 Cl2
b) silver oxide  silver + oxygen
cesium carbonate  cesium oxide + carbon dioxide
h) 2 Al(OH)3  Al2O3 + 3 H2O
2 Ag2O  4 Ag + O2
c) nitrous acid  dinitrogen trioxide + water
aluminium hydroxide  aluminium oxide + water
i)
HNO2  N2O3 + H2O
d) iron (III) hydroxide  iron (III) oxide + water
sulphuric acid  sulphur trioxide + water
j)
2 Fe(OH)3  Fe2O3 + 3 H2O
e) zinc carbonate  zinc oxide + carbon dioxide
carbonous acid  carbon monoxide + water
H2CO2  CO + H2O
2 RbClO3  RbCl2 + 3 O2
rubidium chlorate  rubidium chloride + oxygen
k) 2 LiCl  2 Li + Cl2
ZnCO3  ZnO +CO2
f)
H2SO4  SO3 + H2O
lithium chloride  lithium + chlorine
l)
2 Au(ClO3)3 2 AuCl3 + 9 O2
gold (III) chlorate  gold (III) chloride + oxygen
SCH 3U
Chemical Reactions
B) SYNTHESIS
Name: _________________________
A + B  AB
During a synthesis reaction, two or more elements or simple compounds come together to form 1 compound. These are
the reverse of a decomposition reaction.
Examples:
sodium + oxygen  sodium oxide
Sn + F2  SnF2
lead (II) oxide + carbon dioxide  lead(II) carbonate
K2O + CO2  K2CO3
iron (II) chloride + oxygen  iron (II) chlorate
BeCl2 + 3 O2  Be(ClO3)2
zinc oxide + water  zinc hydroxide
Na2O + H2O  2 NaOH
silicon dioxide + water  silicic acid
SeO2 + H2O  H2SeO3
Since synthesis reactions are the reverse of decomposition reactions, reverse the rules from above to determine the
products of a synthesis reaction.
1.
2.
3.
4.
5.
Two elements will react to form the binary compound.
A metal oxide and carbon dioxide will react to form the metal carbonate.
A metal chloride and oxygen will react to form the metal chlorate.
A metal oxide and water will react to form a metal hydroxide.
A non-metal oxide and water will react to form the oxy acid (with the non-metal having the same valence).
Practice Problems: Provide a completed word and full balanced chemical equation for each reaction.
a) magnesium chloride + oxygen  magnesium chlorate
MgCl2 + 3 O2  Mg(ClO3)2
b) cesium + iodine  cesium iodide
2 Cs + I2  2 CsI
c) diphosphorus trioxide + water  phosphorous acid
g) BeO + CO2  BeCO3
beryllium oxide + carbon dioxide beryllium carbonate
h) Al2O3 + H2O  Al(OH)3
aluminium oxide + water  aluminium hydroxide
i)
P2O3 + 3 H2O  2 H3PO3
d) potassium oxide + water  potassium hydroxide
dinitrogen trioxide + water nitrous acid
j)
K2O + H2O  2 KOH
e) barium oxide + carbon dioxide  barium carbonate
silver + sulfur  silver sulfide
16 Ag + S8  8 Ag2S
NaCl + O2 NaClO3
sodium chloride + oxygen  sodium chlorate
k) Ga + Br2  GaBr3
BaO + CO2  BaCO3
f)
N2O3 + H2O  HNO2
gallium + bromine  gallium bromide
l)
Ca + P4  Ca3P2
calcium + phosphorus  calcium phosphide
SCH 3U
Chemical Reactions
Name: _________________________
C) SINGLE DISPLACEMENT
AX + Y  YX + A or AX + B  AB + X
During a single displacement (also called single replacement) reaction one element replaces another element in a
compound forming a new compound. There are 2 different possibilities.
1. One cation replaces another: AX + Y  YX + A, where both A and Y are cations (usually metals and hydrogen).
For an element to displace another in a compound, it must be higher up in the activity series than the element in
the compound.
Examples:
copper + silver nitrate  silver + copper (II) nitrate
calcium + water  calcium hydroxide + hydrogen
Fe + Cu(NO3)2  Fe(NO3)2 + Cu
Zn + HCl(aq)  ZnCl2 + H2
2. One anion replaces another: AX + B  AB + X, where both X and B are anions (usually non-metals). For an
element to displace another in a compound, it must be more reactive than the element in the compound.
Examples:
chlorine + sodium bromide  sodium chloride + bromine
Br2 + 2 KI  2 KBr + I2
Practice Problems: Provide a completed word and full balanced chemical equation for each reaction.
a) aluminum + lead (II) nitrate  lead + aluminium nitrate
2 Al + 3 Pb(NO3)2  3 Pb + 2 Al(NO3)3
b) chlorine + lithium iodide iodine + lithium chloride
Cl2 + 2 LiI  I2 + 2 LiCl
c) iron + silver acetate silver + iron(II) acetate
Fe + 2 AgC2H3O2  2 Ag + Fe(C2H3O2)2
d) aluminum + copper(II) chloride copper + aluminium chloride
2 Al + 3 CuCl2  3 Cu + 2 AlCl3
e) bromine + iron (III) chloride  No Reaction
Br is less reactive than Cl
f)
barium + water  barium hydroxide + hydrogen
Ba + 2 H2O  Ba(OH)2 + H2
g) 2 Al + 6 HCl(aq)  2 AlCl3 + 3 H2
aluminium + hydrochloric acid  aluminium chloride + hydrogen
h) Zn + H2SO4  ZnSO4 + H2
zinc + hydrochloric acid  zinc sulphate + hydrogen
i)
Pb + 2 AgNO3  2 Ag + Pb(NO3)2
lead + silver nitrate  silver + lead (II) nitrate
j)
Fe + CuSO4  Cu + FeSO4
iron + copper (II) sulphate  copper + iron (II) sulphate
k) 2 Li + 2 H2O  2 LiOH + H2
lithium + water  lithium hydroxide + hydrogen
l)
PbI4 + F2  PbF4 + I2
lead (IV) iodide + fluorine  lead (IV) fluoride + iodine
SCH 3U
Chemical Reactions
D) DOUBLE DISPLACEMENT
Name: _________________________
AB + XY  AY + XB
During a double displacement (also called a double replacement) reaction, the cations and anions of two different
compounds switch places.
Examples:
iron (II) acetate + sodium chloride  iron(II) chloride + sodium acetate
2 NaCl + H2SO4  Na2SO4 + 2 HCl
AgNO3 + NaCl  AgCl + NaNO3
When an acid and base react, this is a special case of a double displacement reaction called a neutralization which forms
a salt (ionic compound) and water.
Examples:
potassium hydroxide + sulfuric acid  potassium sulfate + water
2 H3PO4 + 3 Ca(OH)2  Ca3(PO4)2 + 6 H2O
In some cases, a product will form in the double displacement reaction that will then decompose further. Whenever
H2CO3, H2SO3 and NH4OH are formed in the reaction, they will decompose to CO2 and H2O, SO2 and H2O and NH3 and H2O
respectively.
Examples:
calcium carbonate + hydrochloric acid  calcium chloride + carbon dioxide + water
K2SO3 + 2 HNO3  2 KNO3 + SO2 + H2O
NH4Cl + NaOH  NaCl + NH3 + H2O
Practice Problems: Provide a completed word and full balanced chemical equation for each reaction.
a) calcium hydroxide + carbonic acid  calcium carbonate + water
Ca(OH)2 + H2CO3  CaCO3 + 2 H2O
b) potassium carbonate + barium chloride potassium chloride + barium carbonate
K2CO3 + BaCl2  2 KCl + BaCO3
c) zinc phosphate + ammonium sulfide zinc sulphide + ammonium phosphate
Zn3(PO4)2 + 3 (NH4)2S  3 ZnS + 2 (NH4)3PO4
d) cobaltic hydroxide + nitric acid cobaltic nitrate + water
Co(OH)3 + 3 HNO3  Co(NO3)3 + 3 H2O
e) silver nitrate + potassium chloride silver chloride + potassium nitrate
AgNO3 + KCl  AgCl + KNO3
f) ammonium chloride + magnesium hydroxide magnesium chloride + ammonia + water
NH4Cl + Mg(OH)2  MgCl2 + NH3 + H2O
g) Na2CO3 + H2SO4 Na2SO4 + CO2 + H2O
Sodium carbonate + sulphuric acid  sodium sulphate + carbon dioxide + water
h) Al(OH)3 + 3 HC2H3O2  Al(C2H3O2)3 + 3 H2O
aluminium hydroxide + acetic acid  aluminium acetate + water
i) Al2(SO4)3 + Ca3(PO4)2 2 AlPO4 + 3 CaSO4
aluminum sulfate + calcium phosphate  aluminium phosphate + calcium sulfate
j) Cr2(SO3)3 + 3 H2SO4  Cr2(SO4)3 + 3 H2O + 3 SO2
chromium (III) sulfite + sulfuric acid  chromium (III) sulfate + water + sulfur dioxide
k) 2 AgC2H3O2 + K2CrO4 Ag2CrO4 + 2 KC2H3O2
silver acetate + potassium chromate  silver chromate + potassium acetate
l) (NH4)2SO4 + 2 KOH  K2SO4 + 2 H2O + 2 NH3
ammonium sulfate + potassium hydroxide  potassium sulfate + water + ammonia
SCH 3U
Chemical Reactions
E) COMBUSTION
Name: _________________________
CxHy + O2 (g)  CO2 (g) + H2O (g) or CxHy + O2 (g)  C (s) + CO (g) + CO2 (g) + H2O (g)
In a combustion reaction, a hydrocarbon (a compound made of carbon and hydrogen) reacts with oxygen gas. There are
2 types of combustion.
1. Complete Combustion: CxHy + O2 (g)  CO2 (g) + H2O (g)
2. Incomplete Combustion: CxHy + O2 (g)  C (s) + CO (g) + CO2 (g) + H2O (g)
Examples:
CH4 + O2 (g)  CO2 (g) + 2 H2O (g)
C3H6 + 3 O2 (g)  C (s) + CO (g) + CO2 (g) + 3 H2O (g)
In some cases the hydrocarbon may also contain nitrogen or sulfur, in which case NO2 or SO2 is also produced.
Examples:
C21H24N2O4 + 27 O2 (g)  21 CO2 (g) + 12 H2O (g) + 2 NO2 (g)
2 C2H5SH + 9 O2 (g)  4 CO2 (g) + 6 H2O (g) + 2 SO2 (g)
Practice Problems: Complete a balanced chemical equation for each reaction. Assume complete combustion in each.
a) 2 C6H6 + 15 O2 (g)  12 CO2(g) + 6 H2O(g)
b) C11H22O11 + 22 O2 (g)  22 CO2(g) + 11 H2O(g)
c) C25H52 + 38 O2 (g)  25 CO2(g) + 26 H2O(g)
d) 2 C2H5OC2H5 + 13 O2 (g)  8 CO2(g) + 10 H2O(g)
e) C4H9OH + 6 O2 (g)  4 CO2(g) + 5 H2O(g)
f)
2 C6H13SH + 21 O2 (g)  12 CO2(g) + 14 H2O(g) + 2 SO2(g)
F) EXOTHERMIC AND ENDOTHERMIC
Many reactions require or release heat and in addition to being classified as one of the types discussed above can also
be classified as exothermic or endothermic. Exothermic reactions are those accompanied by a release of heat (energy)
Example:
2 H2(g) + O2(g)  2 H2O(g) + Energy
Endothermic reactions are those that require heat (energy) to be added for the reaction to occur.
Example:
CaCO3(s) + Energy  CaO (s) + CO2 (g)