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Sub-Topic 3.4
Using & Controlling Reaction: Rate of Reaction
| Question | Answer |
|---|---|
| What is the collision theory? | In order for particles to react, they must collide with sufficient energy and the correct orientation. |
| Define activation energy. | The minimum energy required for a reaction to occur. |
| What are the two ways the rate of reaction can be determined? | 1) the change in number of moles per unit time. 2) the change in concentration per unit time. |
| How does the nature of the reactants affect the rate of a reaction? | Reactions involving the contact of ions in solution are generally fast (ie: acid base reactions), whereas those where covalent bonds are broken and then remade are generally slower (ie: combustion) |
| How does the concentration of the reactants affect the rate of a reaction? | A greater concentration is more particles in a given space. There will be more collisions with the correct energy and orientation per unit time so the rate of reaction increases. |
| How does the temperature affect the rate of a reaction? | If the temperature is increased, the particles gain more energy this means that they move faster and so more collisions will occur per unit time, hence a faster rate of reaction. The opposite is true for when the temperature is decreased. |
| How does the size of the particles (state of subdivison) affect the rate of reaction? | If the surface area of the particles is increased, there are more collisions with the correct orientation and required energy so the reaction increases. |
| How does the presence of light affect the rate of reaction? | Light, like heat, provides the particles with more energy, so more collision occur with the correct orientation and the required activation energy, so the rate of reaction increases. E.g. film photography, photosynthesis and ozone formation. |
| How does the presence of a catalyst affect the rate of reaction? | They provide an alternate reaction pathway with a lower activation energy and line up the reactants with the correct orientation to bring about a faster reaction. |
| What are examples of catalysts? | Enzymes, acid/bases in making an ester, platinum metal in catalytic converters and chlorine atoms in the destruction of ozone |
| What does a lower activation energy do? | Allows more particles to have the required activation energy so the reaction is faster. |
| Is a catalyst used up? | No |
| What are the axes in an energy profile graph? | y axis is potential energy and x axis is reaction progress. |
| What are the axes in an energy distribution graph? | y axis is number of particles and x axis is kinetic energy. |
Created by:
MahaliaMcD
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