Objective 3

1
Objective 3

• TSWBAT classify chemical reactions.

2
Synthesis Reactions

• A reaction in which a compound is made from two
  or more species
• General form
• A B ? AB
• Examples
• 2 Mg(s) O2(g) ? 2 MgO(s)
• CaO(s) CO2(g) ? CaCO3(s)

3
Decomposition Reactions

• Reaction in which a compound breaks down into two
  or more species, usually with the addition of
  heat or a catalyst
• General Form
• AB ? A B
• Examples
• 2 H2O(l) ? 2 H2(g) O2(g)
• 2 KClO3(s) ? 2 KCl(s) 3 O2(g)
• 2 H2O2(aq) ? 2 H2O(l) O2(g)

4
Exchange Reactions(also known as
double-replacement reactions)

• Reaction in which there is an exchange of
  cation/anion pairs
• General Form
• AB CD ? AD CB
• Virtually all exchange reactions take place
  between 2 aqueous solutions
• If one species is solid, it will usually dissolve
  in water anyway
• 3 subgroups of exchange reactions
• Precipitation, Gas-forming and Neutralization

5
Precipitation Reactions

• An exchange reaction in which two aqueous
  solutions produce an insoluble solid
  (precipitate)
• AB CD ? AD CB (one of which is solid product)
• Example
• AgNO3(aq) NaCl(aq) ? AgCl(s) NaNO3(aq)

6
Gas-Forming Reactions

• An exchange reaction in which a gas, usually
  carbon dioxide, is formed
• ACO3 HB ? AB H2O CO2
• Example
• Na2CO3(aq) 2 HCl(aq) ? 2 NaCl(aq)
  H2O(l) CO2(g)

7
Neutralization Reactions

• An acid reacts with a base to form water and a
  salt
• HA BOH ? BA H2O
• Example
• Ba(OH)2(s) 2 HCl(aq) ? BaCl2(aq) 2
  H2O(l)

8
Combustion Reactions

• A hydrocarbon combines with oxygen to produce
  carbon dioxide and water
• Example
• CH4(g) 2 O2(g) ? CO2(g) 2 H2O(l)

9
Single Replacement Reactions

• These are actually oxidation-reduction (redox)
  reactions
• They involve an exchange of electrons between
  atoms
• These kind of redox reactions have the form in
  which an element replaces a like element in a
  compound

10

• General Form
• A BC ? AC B (metal replacement)
• A BC ? BA C (halogen replacement)
• Examples
• Fe(s) Cu(NO3)2(aq) ? Cu(s) Fe(NO3)2(aq)
• Cl2(g) 2 NaI(aq) ? I2(s) 2 NaCl(aq)