1. Rate of reaction is defined as the
change in the amount of reactants or products per unit time.
2. It is a measure of how fast a
reaction occurs.
- Fast Reaction = Rate of reaction is
high.
- Slow Reaction = Rate of reaction is low.
3. A fast reaction takes shorter time
for the reaction to complete.
4. Example of fast reaction
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Type of Reaction
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Example
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Combustion
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Combustion of magnesium in oxygen
Mg+O2→MgO
Combustion of ethane (C2H6)
C2H6+72O2→2CO2+3H2O
|
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Reaction between reactive metal and water
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Reaction between potassium and water
2K+2H2O→2KOH+H2
|
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Reaction between metal carbonate and acid
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Reaction between limestone/ marble and sulphuric
acid
CaCO3+H2SO4→CaSO4+CO2+H2O
|
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Ionic precipitation (Double decomposition)
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Precipitation of silver(I) chloride
AgNO3+ HCl→AgCl + HNO3
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Example of slow reaction
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Type of Reaction
|
Example
|
|
Photosynthesis
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6CO2+ 6 H2O→C6H12O6+ 6O2
|
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Rusting
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4Fe+3O2+ 2H2O→2Fe2O3∙H2O
|
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Fermentation
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C6H12O6→2C2H5OH + 2CO2
|
- · The reaction is fastest at the start when the reactants are at a maximum (steepest gradient)
- · The gradient becomes progressively less as reactants are used up and the reaction slows down.
- · Finally the graph levels out when one of the reactants is used up and the reaction stops.
- · The amount of product depends on the amount of reactants used.
- · The initial rate of reaction is obtained by measuring the gradient at the start of the reaction. A tangent line is drawn to measure rate of reaction at instantaneous time.
