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Chemical Reactions:Chapter 9
Reactants change chemical and
physical properties
…. to become new substances made
from the same elements; these
are called products.
Types of Reactions
• Synthesis or Composition• Decomposition• Single Replacement• Double Displacement• Combustion Reactions
Composition/ Synthesis Reactions
• A + X AX• An element may react with oxygen
to form the oxide (oxidation)
A X
Composition/ Synthesis Reactions
• O2 + 2Mg 2 MgO
• oxygen reacts with magnesium to form magnesium oxide
OMg
O
Mg
Composition/ Synthesis Reactions
• C + O2 CO2
• carbon reacts with oxygen to form carbon dioxide
O C
O
Practice predicting reactions with oxide and sulfides
1. 2Fe + ____ 2FeO
2. 4 Fe + 3 ___ Fe2O3
3. S8 + 8 O2 8 ____
4. 8 Ba + S8 8 ____
O2
O2
SO2
BaS
Metals react with halogens.
• 2Na + Cl2 2 NaCl• 2 Co + 3 F2 2 CoF3
• 2 K + I2 2 KI• Sr + Br2 SrBr2
• 2Mg + O2 2 MgO
Synthesis reactions can also occur with oxides.• Active metal oxides react with water to form
hydroxides. ex:• CaO + H2O Ca(OH)2
• Many oxides of nonmetals react with water to form oxyacids. ex:
• SO2 + H2O H2SO3
• Some metal oxides react with nonmetal oxides to form salts.
• CaO + SO2 CaSO3
Practice
• Active metal oxides react with water to form hydroxides. ex:
• MgO + H2O ________• Many oxides of nonmetals react with
water to form oxyacids. ex:• SO3 + H2O _________
• Some metal oxides react with nonmetal oxides to form salts.
• MgO + NO2 ________
Mg(OH)2
H2SO4
Mg(NO3)2
DecompositionAX A + X
• 2H2O 2H2 + O2
O
H
H
O
H
HElectrolysis: decomposition of a substanceby an electric current.
DecompositionAX A + X
• 2HgO 2Hg + O2
OHg
OHg
This reactionoccurs when youheat orange coloredmercury (II) oxide.
Silver mercury and oxygen gas form.
Decompositionof metal carbonatesACO3 AO + CO2 (g)• CaCO3 (s) CaO (s) + CO2 (g)
OCa
O
This reactionoccurs when youheat calcium carbonate.
calcium oxide and carbondioxide form.
O
C
Decompositionof metal hydroxidesAOH AO + CO2 (g)• Ca(OH)2 (s) CaO (s) + H2O (g)
H
Ca
O
This reactionoccurs when youheat calcium hydroxide
calcium oxide and waterform.
OH
Decomposition of metal chloratesAClO3 ACl + O2 (g)
• 2KClO3 (s) 2KCl (s) + 3O2 (g)
K
O
This reactionoccurs when youheat potassium chlorate.
potassium chloride and oxygen form.
Cl
OK
O
O
ClO
O
Decomposition of acidsH2CO3 (aq) H2O (g) + CO2 (g)
Carbonic aciddecomposes whenwarmed.
water and carbon dioxide form.
O
OO
C
HH
Single DisplacementA+ BX AX + Bor:Y + BX BY + X• Replacement of a metal in a compound by another
metal.
2 Al (s) + 3Pb(NO3)2 3Pb +2 Al(NO3)3
Al
Al
Pb2+
N
O
OO
N
O
O
O
NO
O
O
NO
O
O
N
O
O
O
NO
O O
Pb2+
Pb2+
Single DisplacementA+ BX AX + Bor:Y + BX BY + X• Replacement of a metal in a
compound by another metal.2 Al (s) + 3Pb(NO3)2 3Pb +2 Al(NO3)3
Al3+Al3+
Pb
N O
O
OPb
N O
O
O
Pb
NO
O O
NO
O
O
NO
OO
NO
O O
Single DisplacementA+ BX AX + Bor:Y + BX BY + X• Replacement of a hydrogen in a
compound by a metal.2 Na (s) + 2 H2O (l) 2 NaOH (aq) + H2 (g)
Na
NaO
H
H
O
H
H
Single DisplacementA+ BX AX + Bor:Y + BX BY + X• Replacement of a hydrogen in a
compound by a metal.Mg (s) + 2 HCl (aq) MgCl2 (aq) + H2 (g)
Mg
Cl
H
Cl
H
Single DisplacementA+ BX AX + Bor:Y + BX BY + X• Replacement of halogens
Cl2 (g) + 2 KBr (aq) 2 KCl (aq) + Br2 (g)
ClK
Br
Br
K
Cl
Double Replacement Reactions (double displacement)• Formation of a precipitate.• 2 KI (aq) + Pb(NO3)2 (aq) PbI2 (s) + 2 KNO3 (aq)
K
K
I
Pb2+
N
O
OO
NO
OO
I
Double Replacement Reactions (double displacement)• Formation of a gas.• FeS (s) + 2 HCl(aq) H2S (g) + FeCl2 (aq)
Fe2+S
Cl
H
Cl
H
Double Replacement Reactions (double displacement)• Formation of a water.• NaOH (s) + HCl(aq) H2O (g) + NaCl2 (aq)
Na+
Cl
H
OH
Combustion Reactions
• A substance combines with oxygen, releasing a large amount of energy in the form of light and heat.
2 H2 (g) + O2 (g) 2 H2O
O
H
H
O
H
H
Combustion Reactions• A substance combines with oxygen, releasing a
large amount of energy in the form of light and heat.
C3H8 (g) +5 O2 (g) 4 H2O + 3 CO2
CC C
H
H
HH
H
HH
HO
OO
O
O
O
OO
O
O
Combustion Reactions• A substance combines with oxygen, releasing a
large amount of energy in the form of light and heat.
C3H8 (g) +5 O2 (g) 4 H2O + 3 CO2
C
C
C
HH
H
H
HH
H
H O
OO
O
O
O
OO
O
O
