Collision Theory & Rate

• What is the collision theory?

  For a reaction to occur, the particles need to collide with each other at the right orientation with enough energy
• What is activation energy?

  Activation energy is the minimum amount of energy required for a chemical reaction to occur.
• What is a catalyst?

  • A catalyst is a substance that increases the rate of reaction without taking part in the chemical reaction by providing the particles an alternative pathway with a lower activation energy. It is not used up in a reaction.
• Why does increasing temperature increase rate of reaction?

  The particles move faster - so they collide more frequently leading to more successful collisions

  The particles have the activation energy or more - so they collide successfully more often
• Why does increasing concentration increase rate of reaction?

  There are more particles in a given volume - so particles collide more frequently
• Why does increasing pressure increase rate of reaction?

  There is less space for particles to move - so there are more frequent collisions
• What is a homogenous catalyst?

  The catalyst is in the same state as the reactants
• What is a heterogenous catalyst?

  A catalyst that is in a different state to the reactants
• Why are heterogenous catalysts favoured?

  They are easy to separate from the reactants
• What is rate of reaction?

  The change in product/time
• Explain this graph:

  1. Hydrogen is produced quickly as there is a high concentration of reactants
  2. Rate of reaction slows as concentration of reactants decreases
  3. The graph plateaus at 90s as the reactants are used up

  
• What are the energies like in an exothermic reaction?

  The reactants have higher energy than the products
• What are the energies like in an endothermic reaction?

  The products have higher energy than the reactants