Chemistry2 Rates of Reaction xox

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Collision Theory

  • chemical reactions only occur when reacting particles collide with sufficient energy
  • ACTIVATION ENERGY = the minimum amount of energy needed by the particles to react
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Rate Of Reaction

  • the rate of reaction depends on things: 
  • 1) Temperature
  • 2) Concentration/pressure    
  • 3) Catalyst
  • 4) Surface area
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Temperature

When the temp is increased:

  • the particles gain heat energy
  • therefore gaining kinetic energy
  • so they move quicker
  • and collide more frequently
  • with greater energy
  • so MORE SUCCESSFUL COLLISIONS

The rate of reaction also increases.

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Concentration/Pressure

In a solution, when the concentration increases:

  • there are more particles
  • which collide more frequently
  • so MORE SUCCESSFUL COLLISIONS

The rate of reaction also increases.

In a gas, when the pressure increases:

  • the particles are closer together
  • so they collide more frequently
  • so MORE SUCCESSFUL COLLISIONS

The rate of reaction also increases.

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Surface Area

As the surface area increases:

  • more particles are exposed/available for collisions
  • so they collide more frequently
  • meaning MORE SUCCESSFUL COLLISIONS

The rate of reaction also increases.

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Catalyst

CATALYST = a substance which speeds up a reaction without being used up (or altered)    in the reaction

  • reduces the activation energy
  • so means more particles can collide successfully 
  • so speeding up the reaction
  • it provides a surface for the particles to attach to- increasing their chances of colliding 

Therefore the rate of reaction increases.

ADVANTAGES:

  • reduces costs - can allow the reaction to work at a much lower temperature (reduces energy)
  • reduces time - the rate of reaction is increased so more product produced quicker

DISADVANTAGES

  • dif. reactions use dif. catalysts - e.g. manufacture of ammonia uses iron catalyst but hydrocarbons for example use broken pottery                                     
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