Types of Chemical Reactions

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Types of Chemical Reactions
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Evidence of Chemical Reactions

1. Change in colour
2. Change in odour
3. Formation of a gas
4. Formation of a precipitate
5. Release or absorption of energy (e.g. heat or
   light)

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Types of Chemical Reactions

• We will learn about 6 types of chemical reactions
• Synthesis
• Decomposition
• Combustion
• Single Displacement
• Double Displacement
• Neutralization

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Subscripts for States of Matter

• We can identify the physical state of a substance
  using subscripts
• (s) solid
• (g) gas
• (l) pure liquid
• (aq) aqueous solution (dissolved in water)

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Synthesis Reactions

• Smaller atoms/molecules combine to form larger
  molecules

A B ? AB
2H2(g) O2(g) ? 2H2O(l)
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Synthesis Reaction

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Decomposition Reaction

• The splitting of a large molecule into elements
  or smaller molecules

AB ? A B
Complimentary to synthesis reaction
2H2O(l) ? 2H2(g) O2(g)
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Decomposition Reaction

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Combustion

• Fuel (hydrocarbons) burned in the presence of
  oxygen to produce a carbon dioxide, water and
  heat energy

CxHy O2 ? CO2 H2O heat
C4H10(l) O2(g) ? CO2(g) H2O(l) heat
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Incomplete Combustion

• Occurs when fuel is not completely converted into
  carbon dioxide and water
• Can result in the production of toxic carbon
  monoxide

C4H10(l) O2(g) ? C(s) CO(g) CO2(g)
H2O(g)
soot
poisonous
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Single Displacement

• One element replaces another element from a
  compound

A BC ? AC B
Mg(s) 2AgNO3(aq) ? 2Ag(s) Mg(NO3)2(aq)
Note A metal can only replace a metal and a
nonmetal can only replaces a nonmetal
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Single Displacement
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Single Displacement


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The Activity Series
If the single element is above the element in the
compound, a single displacement reaction will
occur.
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Examples

1. aluminum nickel (II) chloride
2. lead zinc nitrate
3. fluorine sodium bromide

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Double Displacement

• Positive ions (cations) in different compounds
  replace each other

AB CD ? AD CB
Pb(NO3)2(aq) 2KI(aq) ?PbI2(s) 2KNO3(aq)
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Double Displacement
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Double Displacement


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Solubility Rules

• Most double displacement reactions involve
  aqueous solutions of ionic compounds
• For a reaction to occur, a precipitate (insoluble
  solid) must form
• To predict which ionic compounds will be soluble,
  and which will form precipitates (insoluble) we
  must use the solubility rules

1. All compounds with nitrate (NO3-) are soluble
2. All compounds with ammonium (NH4) are soluble
3. All compounds with group 1 metals are soluble
4. Most other compounds are insoluble (will form a
   precipitate)

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Solubility Table

• Or use a solubility table

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Examples

1. sodium carbonate barium nitrate ?
2. lithium hydroxide ammonium chlorate ?

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Neutralization

• A special type of double displacement reaction

Acid Base ? Salt H2O
(ionic compound)
HCl(aq) NaOH(aq) ? NaCl(aq) H2O(l)
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Practice Makes Perfect!

• Read p. 111, 114-115,118-123,138-139
• Try some problems.