1. Reaction Types

2. Classifying Reactions
• There are millions of substances and
many different possible reactions
• There are only a few general reaction
types
• Just like there are ways to identify
the names of compounds, there are
ways to identify types of chemical
reactions and predict the products

3. Synthesis Reactions
• Combine substances
• Reaction of at least 2 reactants
combine to form a product
• A + B -- AB
• Always join substances so the
product is more complex than the
reactant

4. Decomposition Reactions
• Break substances apart
• Reaction in which one compound reaks
into at least 2 products
• AB -- A + B
• 2H2O -- 2H2 + O2

5. Combustion Reactions
• Use oxygen as a reactant
• Oxygen is a reactant in EVERY
combustion reaction

6. Single Displacement
Reactions
• Elements trade places
• XA + B -- BA + X
• Usually, a more reactive element
takes the place of a less reactive
element

7. Double-Displacement
Reaction
• Reaction in which a gas, solid
precipitate, or a molecular compound
is formed
• Ions appear to be exchanged between
compounds
• AX + BY -- AY + BX

8. Electrons and Chemical
Reactions
• Classes of reactions (Synthesis,
Decomposition, Combustion, Single-
Displacement, Double Displacement)
used by early chemist before atom
was understood
• Today, reactions can be classified by
understanding the transfer of
electrons

9. Redox Reactions
• Reduction/Oxidation Reaction
• A reaction that occurs when
electrons are transferred from one
reactant to another
• Substances that accept electrons are
reduced (gain e- reduces + charge)
• Substances that give up electrons are
oxidized

10. Summary
• Synthesis reactions make larger
molecules
• Decomposition breaks compounds
apart
• In combustion reactions, substances
react with oxygen
• Elements appear to trade places in
single-displacement reactions

11. Summary cont...
• In double-displacement reactions,
ions appear to move between
compounds, resulting in a solid that
settles out in solution, a gas that
bubbles out of a solution, and/or a
molecular substance
• In redox reactions, electrons are
transfer from one substance to
another

12. Question 1
• Classify each of the following
reactions by type
– A) S8 + 8O2 -- 8SO2 + heat
– B) 6CO2 + 6H2O -- C6H12O6 + 6O2
– C) 2NaHCO3 -- Na2CO3 + H2O + CO2
– D) Zn + 2HCl -- ZnCl2 + H2

13. Question 2
• Identify which element is oxidized
and which element is reduced in the
following reaction
– Zn + CuSO4 -- ZnSO4 + Cu

14. Question 3
• Compare and contrast single-
displacement and double-displacement
reactions based on the number of
reactants.
• Use the terms compound, atom,
element, and ion.