■ Collision theory
► | A chemical reaction may occur as a result of the collisions between particles. | |
► | For a reaction to occur, an effective collision must take place. |
► | The particles of the reactants must collide with each other to produce energy that greater than or equal to the activation energy. | |
► | The collisions must happen in the correct orientation. | |
► | The animation below shows the collisions of particles.
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► | Minimum amount of energy required to initiate a chemical reaction. | |||
► | Energy profile diagram can be used to shows the energy change that takes place in a chemical reaction.
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► | This video contains information on the effective collision and activation energy.
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► | Example: Reaction of hydrogen with iodine to produce hydrogen iodide. H2(g) + I2(g) → 2HI(g) |
► | Relationship of frequency of effective collisions and rate of reaction
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► | Relationship of activation energy and rate of reaction
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Collision theory and the effect of surface area (particle size)
■ The effect of the size of reactant
► | If the size of the solid material that reacts is small, the amount of surface area exposed to reaction increased. | |
► | The chance for collisions increased, the collision frequency is also increased, resulting in the increased of effective collisions. | |
► | The rate of reaction also increased. | |
► | The animation below shows the effect of size of reactant on the rate of reaction.
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Collision theory and the effect of concentration
■ The effect of concentration
► | When the concentration increases, the number of particles per unit volume increases. | |
► | Therefore, the total number of collisions and the effective collision frequency between particles of materials response will increase. | |
► | Thus, the reaction rate increases. | |
► | The animation below shows the effect of concentration on the rate of reaction.
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Collision theory and the effect of temperature
■ The effect of temperature
► | When the reaction temperature increased, the particles of the reactants have more kinetic energy. | |
► | Particles reactants move more quickly. | |
► | This increases the chances of a collision, the collision frequency is increased. | |
► | Then the effective collision frequency increases and the rate of reaction increases. | |
► | The animation below shows the effect of temperature on the rate of reaction.
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Collision theory and the effect of catalyst
■ The effect of catalyst
► | Catalysts change the rate of a reaction by varying the activation energy of the reaction. |
► | Provide a reaction path requires a lower activation energy. | |
► | More particles will have enough energy to overcome the lower activation energy. | |
► | The effective collision frequency is increased. | |
► | Thus, it accelerate the rate of a reaction.
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► | Delay the rate of reaction by increasing the activation energy of the reaction so that the effective collision frequency is reduced. |
Pressure and rate of reaction
■ The effect of pressure
► | When pressure increase, the particles are close together. | |
► | The number of particles per unit volume increases. | |
► | Frequency of collisions between particles increase, higher frequency of effective collisions. | |
► | More particles have activation energy, thus the rate of reaction increase. | |
► | The animation below shows the effect of pressure on the rate of reaction.
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⇲ For exercise(objective and subjective), download for free on Android OS. | |
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