Chemical Reactions: Chapter 7 (Chapter outline due Tuesday)

1
Chemical ReactionsChapter 7(Chapter outline
due Tuesday)

• Reactants change chemical and physical properties

. to become new substances made from the same
elements these are called products.
2
When you write a chemical reaction

• The word equation explains what you begin with,
  and what you have at the end of the reaction.
• The reactants FORM, YIELD, or MAKE the products.
• Physical states may be included
• (aq) aqueous
• (l) liquid
• (s) or (cr) solid or crystalline
• (g) gaseous

Example solid sodium reacts with water to form
aqueous sodium hydroxide and hydrogen gas.
3
Types of Reactions

• Synthesis or Composition
• Decomposition
• Single Replacement
• Double Displacement
• Combustion Reactions

A B ? AB
HONCl BrIF A new twist To writing
Formulas. These are Always written As
diatomic Molecules.
AB ? A B
AB C ? AC B
AB CD ? AD CB
CxHy O2 ? CO2 H2O
4
Writing Equations

• Subscripts describe the chemical composition of
  the substance. These are determined by the
  electrons in the atoms and MAY NOT BE CHANGED
  when balancing equations.
• Coefficients are used to balance equations.

Na Cl2 ? NaCl
2
2
5
Composition/ Synthesis Reactions

• A X ? AX
• An element may react with oxygen to form the
  oxide (oxidation)

X
A
6
Composition/ Synthesis Reactions

• O2 2Mg ? 2 MgO
• oxygen reacts with magnesium to form magnesium
  oxide

Mg
O
O
Mg
7
Composition/ Synthesis Reactions

• C O2 ? CO2
• carbon reacts with oxygen to form carbon dioxide

O
C
O
8
Practice predicting reactions with oxide and
sulfides
O2

1. 2Fe ____ ? 2FeO
2. 4 Fe 3 ___ ? 2 Fe2O3
3. S8 8 O2 ? 8 ____
4. 8 Ba S8 ? 8 ____

O2
SO2
BaS
9
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

10
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

11
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.
• Na2 O 2NO2 ? ________

Mg(OH)2
H2SO4
2 NaNO3
12
DecompositionAX ? A X

• 2H2O ? 2H2 O2

H
O
H
H
O
H
Electrolysis decomposition of a substance by an
electric current.
13
DecompositionAX ? A X

• 2HgO ? 2Hg O2

Hg
O
This reaction occurs when you heat orange
colored mercury (II) oxide. Silver mercury and
oxygen gas form.
Hg
O
14
Decompositionof metal carbonatesACO3 ? AO CO2
(g)

• CaCO3 (s) ? CaO (s) CO2 (g)

O
Ca
This reaction occurs when you heat calcium
carbonate. calcium oxide and carbon dioxide form.
C
O
O
15
Decompositionof metal hydroxidesAOH ? AO CO2
(g)

• Ca(OH)2 (s) ? CaO (s) H2O (g)

H
O
Ca
This reaction occurs when you heat calcium
hydroxide calcium oxide and water form.
O
H
16
Decomposition of metal chloratesAClO3 ? ACl O2
(g)

• 2KClO3 (s) ? 2KCl (s) 3O2 (g)

O
O
Cl
K
Cl
O
K
O
This reaction occurs when you heat potassium
chlorate. potassium chloride and oxygen form.
O
O
17
Decomposition of acidsH2CO3 (aq) ? H2O (g) CO2
(g)
O
H
H
C
Carbonic acid decomposes when warmed. water and
carbon dioxide form.
O
O
18
Single DisplacementA BX? AX BorY BX ? BY
X

• Replacement of a metal in a compound by another
  metal.

2 Al (s) 3Pb(NO3)2 ? 3Pb 2 Al(NO3)3
Pb2
Al
Pb2
Al
Pb2
19
Single DisplacementA BX? AX BorY BX ? BY
X

• Replacement of a metal in a compound by another
  metal.

2 Al (s) 3Pb(NO3)2 ? 3Pb 2 Al(NO3)3
Pb
Al3
Al3
Pb
Pb
20
Single DisplacementA BX? AX BorY BX ? BY
X

• Replacement of a hydrogen in a compound by a
  metal.

2 Na (s) 2 H2O (l) ? 2 NaOH (aq) H2 (g)
H
Na
O
Na
H
H
O
H
21
Single DisplacementA BX? AX BorY BX ? BY
X

• Replacement of a hydrogen in a compound by a
  metal.

Mg (s) 2 HCl (aq) ? MgCl2 (aq) H2 (g)
Cl
Mg
H
Cl
H
22
Single DisplacementA BX? AX BorY BX ? BY
X

• Replacement of halogens

Cl2 (g) 2 KBr (aq) ? 2 KCl (aq) Br2 (g)
Br
Cl
K
Cl
Br
K
23
Double Replacement Reactions (double displacement)

• Formation of a precipitate.
• 2 KI (aq) Pb(NO3)2 (aq) ? PbI2 (s) 2 KNO3 (aq)

I
Pb2
I
K
K
24
Double Replacement Reactions (double displacement)

• Formation of a gas.
• FeS (s) 2 HCl(aq) ? H2S (g) FeCl2 (aq)

S
Fe2
Cl
Cl
H
H
25
Double Replacement Reactions (double displacement)

• Formation of a water.
• NaOH (s) HCl(aq) ? H2O (g) NaCl (aq)

H
O
Na
Cl
H
26
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
O
H
H
H
27
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

O
O
O
O
H
O
H
H
C
H
O
C
C
O
H
O
H
H
O
H
O
28
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

O
C
H
O
O
O
H
H
H
O
H
H
O
C
H
O
O
C
O
O
H