Chapter 24 Lesson 3

1
Chapter 24 Lesson 3

• Classifying Chemical Reactions

2
Types of Reactions

• Chemists have defined five main categories
• combustion
• synthesis
• decomposition
• single displacement
• double displacement

3
Combustion Reactions

• Combustion reaction.
• occurs when a substance reacts with oxygen to
  produce energy in the form of heat and light.
• also produce one or more products that contain
  the elements in the reactants

4
Combustion

• The burning of a substance in O2 to produce heat
• Hydrocarbons (CxHy) always form CO2 and H2O

CxHyO2 ? CO2H2O
CH4 2O2 ? CO2 2H2O
5
Synthesis

• the combination of 2 or more substances to form a
  compound
• only one product forms

A B ? AB
2P 3Br2 ? 2PBr3
6
Decomposition Reactions

• A decomposition reaction
• reverse of a synthesis
• decomposition reaction occurs when one substance
  breaks down, or decomposes, into two or more
  substances
• most require the use of heat, light, or
  electricity.

7
Decomposition

• a compound breaks down into 2 or more simpler
  substances
• only one reactant

AB ? A B
2H2O2 ? 2H2O O2
8
Single Replacement

• one element replaces another in a compound
• metal replaces metal ()
• nonmetal replaces nonmetal (-)

A BC ? AC B
Zn 2HCl ? ZnCl2 H2
9
The Activity Series

• Predict
• which metal will replace another using the
  diagram
• lists metals according to how reactive they are
• A metal
• replace any less active metal.

10
Double Replacement

• ions in two compounds change partners
• cation() of one compound combines with anion(-)
  of the other

AB CD ? AD CB
2KOH CuSO4 ? K2SO4 Cu(OH)2
11
Double Displacement

• Double displacement reaction
• takes place if a precipitate, water, or a gas
  forms when two ionic compounds in solution are
  combined.
• Precipitate
• insoluble compound that comes out of solution
  during this type of reaction.

12
Oxidation-Reduction Reactions

• Gain or loss of electrons
• characteristic that is common to many chemical
  reactions
• Oxidation
• describes the loss of electrons and the term
  reduction to describe the gain of electrons.

13
Oxidation-Reduction Reactions

• Chemical reactions involving electron transfer
• often involve oxygen, which is very reactive,
  pulling electrons from metallic elements.
• Corrosion of metal is a visible result.

14
Oxidation-Reduction Reactions

• Reduced
• gains an electron or electrons obviously becomes
  more negative
• Oxidized
• the substance that loses an electron or electrons
  then becomes more positive

15
Oxidation-Reduction Reactions

• Reduction
• electrons that were pulled from one atom were
  gained by another atom in a chemical reaction
• Redox
• Reduction is the partner to oxidation the two
  always work as a pair