Rates of Reaction

• How does the number of reactant molecules affect the rate of reaction over time?

  A large number of reactant molecules leads to more collisions per second, while fewer molecules lead to fewer collisions
• How does concentration affect the rate of reaction?

  • Higher concentration leads to more particles in the same volume
  • More particles result in more collisions per second
  • Rate of reaction is proportional to concentration
• What is the relationship between the quantity of product and the concentration of reactants?

  A higher concentration leads to a faster reaction and more product at the end
• How can you tell from a graph that a reaction with higher concentration is faster?

  The line representing the higher concentration will be steeper
• How does the surface area of a solid reactant affect the rate of a reaction?

  A greater surface area allows for more collisions per second, increasing the rate
• What happens to the particles in a solid reactant that are not on the surface?

  They cannot react with the particles in solution
• What is the effect of splitting a solid reactant into two blocks?

  It increases the surface area available for reaction
• What is the relationship between surface area to volume ratio and reaction rate?

  Smaller blocks have a greater surface area to volume ratio, leading to more collisions
• How can the effective surface area be investigated in a practical setup?

  • Use marble chips (calcium carbonate) reacting with hydrochloric acid
  • Measure the volume of carbon dioxide produced
  • Change the surface area of the marble chips
• What is a more accurate method for measuring gas volume in a reaction?

  Using a gas syringe
• How can the mass of carbon dioxide gas produced be measured in a reaction?

  • Place the reaction on a balance
  • Measure the decrease in mass as carbon dioxide is produced
  • Calculate the rate of reaction based on mass loss
• What role does cotton wool play in the experimental setup?

  It allows carbon dioxide to escape while preventing acid from splashing out
• What could happen if acid splashes out of the flask during the experiment?

  It could cause the mass to fall more than it should, leading to anomalous results
• What does collision theory state about chemical reactions?

  Chemical reactions can only occur when reacting particles collide with sufficient energy
• How is the rate of a reaction determined according to collision theory?

  By the frequency of successful collisions
• What is meant by "sufficient energy" in the context of collisions?

  It refers to the minimum energy required for particles to collide successfully
• What is the energy profile for a reaction that shows the product has less energy than the reactants?

  It indicates that the reaction is exothermic
• What does the activation energy represent in a chemical reaction?

  The minimum amount of energy that particles must have to react
• What happens to the energy of particles during a chemical reaction?

  Some particles have more energy than others
• What occurs when two particles with low energy collide?

  They cannot overcome the activation energy barrier, so no reaction occurs
• What happens when two particles with high energy collide?

  They can overcome the activation energy barrier and react successfully
• How does increasing the temperature affect the rate of chemical reactions?

  It increases the rate by increasing the energy and speed of particles
• Why does increasing temperature lead to more successful collisions?

  Because particles move faster and have more energy to overcome the activation energy barrier
• What can we say about the relationship between the rate of reaction and temperature?

  The rate of reaction is proportional to the temperature
• What are the key points about the effect of temperature on the rate of a chemical reaction?

  • Increasing temperature increases particle energy
  • Faster particle movement leads to more collisions
  • More collisions result in a higher rate of reaction
  • Rate of reaction is proportional to temperature
• What does collision theory state?

  Chemical reactions can only occur when reacting particles collide with sufficient energy
• What determines the rate of a chemical reaction?

  The frequency of successful collisions
• What is activation energy?

  The minimum amount of energy that particles must have in order to react
• How do catalysts affect the activation energy of a reaction?

  Catalysts provide a different pathway with a lower activation energy
• Can catalysts be reused after a reaction?

  Yes, catalysts are not used up during the reaction
• How do catalysts increase the rate of reaction?

  By allowing more particles to successfully collide per second
• What is the effect of a catalyst on the energy profile of a chemical reaction?

  • Catalysts lower the activation energy required for the reaction
  • More particles can successfully collide per second
  • This increases the rate of the reaction
• What are the key points about catalysts that need to be learned?

  • Catalysts increase reaction rates but are not consumed
  • Not included in chemical equations
  • Different reactions require different catalysts
  • Enzymes act as catalysts in living organisms