Investigating Chemical Reactions

1
Investigating Chemical Reactions

• Chapter 6

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Some very important chemical reactions

• 6CO2 6H2O energy ? C6H12O6 6O2
• 6O2 C6H12O6 ? 6CO2 6H2O energy
• N2 4H2 ? 2NH4
• N2 3O2 ? 2NO3-

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Classifying Reactions

• One way is to use energy considerations
• A reaction such as photosynthesis requires
  energy. It is called endothermic
• A reaction which produces energy is called
  exothermic

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Exothermic and Endothermic reactions

• In a chemical equation, if energy is added to the
  reactants, then it is endothermic
• If energy is added to the products in the
  equation, then the reaction is exothermic
• thermic refers to thermal or heat energy
• Other forms of energy such as light and sound may
  be observed in a chemical reaction

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Some examples

• 2H2O (l) energy ? 2 H2 (g) O2 (g)
  endothermic
• 2 H2 (g) O2 (g) ? 2H2O (l) energy -
  exothermic

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Law of conservation of Energy

• The total energy before a reaction takes place
  must be the total energy after the reaction takes
  place.
• Energy may be transformed from one form to
  another but it is never lost or destroyed.

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4 Reaction Types

• Synthesis
• Decomposition
• Single Displacement
• Double Displacement

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Examples

• 2 H2 (g) O2 (g) ? 2H2O (l) energy synthesis
• 2H2O (l) energy ? 2 H2 (g) O2 (g)
  decomposition
• 2Na (s) 2H2O (l) ? 2 NaOH (aq) H2 (g)
  thermal energy single displacement
• Ba(OH)2 (aq) H2 (g) thermal energy double
  displacement

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Reactions Involving Carbon Compounds

• The study of carbon compounds and their
  properties is called organic chemistry
• Some carbon compounds such as CO2 and CO are
  excluded
• Hydrocarbons are compounds containing carbon and
  hydrogen and are extremely important to us as
  fuels- gasoline, home-heating oil, jet fuel etc

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Combusting Hydrocarbonz

• Complete combustion
• Hydrocarbon O2 (g) ? CO2 (g) H2O (g) energy
• Incomplete combustion
• Hydrocarbon O2 (g) ? CO2 (g) H2O (g) C (s)
  CO (g) energy

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Some basic hydrocarbons

• CH4 methane
• C2H6 ethane
• C3H8 propane
• C4H10 butane

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Good bye Chapter 6

• Hello Acids Bases