CHEMICAL REACTIONS

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CHEMICAL REACTIONS

• A chemical reaction can be observed or has taken
  place when
• a) a gas is given off
• b) a precipitate is formed
• c) change of color
• d) change in energy ( this could be manifested
  as light or heat)

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• Classification of Chemical Equations
• Chemical equations can be classified into six
  simple types
• combination reactions
• decomposition reactions
• single replacement reactions
• d) double replacement reactions
• neutralization reactions
• oxidation-reduction reactions
• f) combustion reactions

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• Examples of decomposition reactions
• The general form is compound    element
  element
• 2H2O    2H2 O2
• H2CO3    H2O CO2

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Combination reactions - two or more substances
(either elements or compounds) react to produce
one substance. These reactions are also called
synthesis reactions. A
B ---gt AB
2 Mg O2 ---gt 2 MgO C O2 (excess) ---gt
CO2 H2O MgO ---gt Mg(OH)2 2 Na Cl2 ---gt 2
NaCl
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Combination Reactions
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• Examples
• The general form is
• element compound    compound element
• Zn 2HCl    ZnCl2 H2
• 2Na 2H2O    2NaOH H2

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• Examples of double displacement reactions
• The general form is compound compound   
  compound compound
• 2KCl Pb(NO3)2    2KNO3 PbCl2

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Double displacement reactions
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Neutralization reaction - the reaction of an acid
with a base to produce salt and water.
HCl NaOH ---gt NaCl H2O

• Examples of combustion reactions
• The general form is hydrocarbon oxygen   
  carbon dioxide water
• CH4 2O2    CO2 2H2O
• C7H16 11O2    7CO2 8H2O

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The reaction between methane and oxygen.
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Oxidation-Reduction reactions - chemical
reactions in which a transfer of electrons occur
are classified as oxidation-reduction reaction or
redox reaction. Na(s) 1/2 Cl2 (g) ----gt
NaCl(s)
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