Chemistry reaction rates

• What does a reaction rate graph show at the start?

  The reaction is fastest (steepest gradient)
• What happens to the reaction rate as time progresses?

  The reaction begins to slow down
• When does a reaction eventually stop?

  When the line becomes horizontal
• Why do reactions slow down over time?

  Because the concentration of reactants is decreasing
• What causes reactions to end?

  The limiting reactant runs out
• How can the overall rate of a reaction be calculated?

  By dividing total product by total time
• How can the rate of a reaction be found at a specific time?

  By finding the gradient of the graph
• What is needed to find the gradient at a curved point on a graph?

  A tangent needs to be drawn at that point
• How can reaction rates be calculated?

  • Amount of reactant used up / time
  • Amount of product / time
• In what units can amounts of reactants and products be measured?

  g, cm³, or moles
• What are the units for the rate of a reaction?

  g/s, cm³/s, or moles/s
• How can slow reactions be timed?

  In minutes or hours instead of seconds
• What is required for a reaction to occur according to collision theory?

  Particles must collide with sufficient energy
• What does the rate of a reaction depend on?

  The frequency of successful collisions
• How can the rate of a reaction be increased?

  • Increasing temperature
  • Increasing concentration or pressure
  • Increasing surface area of solids
  • Adding a catalyst
• What happens when temperature is increased in a reaction?

  Particles move faster and collide more
• What does increasing concentration or pressure do to a reaction?

  It increases the number of particles in space
• How does increasing surface area affect reaction rates?

  More particles are exposed to collide
• What does a catalyst do to a reaction?

  It lowers the activation energy
• Is a catalyst changed during a reaction?

  No, a catalyst is not changed
• What are the key points about catalysts?

  • Specific to one reaction
  • Not changed in a reaction
  • Lower activation energy