Rates of reaction

• What is the relationship between the frequency of successful collisions and the reaction rate?

  The greater the frequency of successful collisions, the greater the reaction rate.
• What does the rate of a reaction measure?

  The rate of a reaction measures how quickly a reactant is used up or a product is formed.
• What is required for a chemical reaction to occur according to collision theory?

  Reactant particles must collide with each other and have enough energy to react.
• What is a successful collision?

  A successful collision is a collision between reactant particles that has enough energy for a reaction to happen.
• What is activation energy?

  Activation energy is the minimum amount of energy that colliding particles must have for them to react.
• How does the activation energy vary?

  The activation energy is different for different reactions.
• What are the two equations to calculate the mean rate of reaction?

  • \(mean~rate~of~reaction = \frac{quantity~of~reactant~used}{time~taken}\)
  • \(mean~rate~of~reaction = \frac{quantity~of~product~formed}{time~taken}\)
• When is measuring mass a useful method in a reaction?

  Measuring mass is useful when carbon dioxide is a product that leaves the reaction container.
• What units are typically used for measuring the rate of reaction when measuring mass?

  The units for rate are usually g/s or g/min.
• How can the volume of a gas be measured during a reaction?

  The volume of a gas can be measured using a gas syringe or an upside-down burette.
• What units are typically used for measuring the rate of reaction when measuring volume?


  The units for rate are usually cm$^3$ s$^{-1}$ or cm$^3$ min$^{-1}$.
• How can the rate of reaction be analyzed graphically?

  • Plot a graph of mass or volume of product formed against time.
  • The steeper the line, the greater the rate of reaction.
  • Faster reactions finish sooner than slower reactions.
• What does the gradient of the line on a reaction rate graph represent?

  The gradient of the line is equal to the rate of reaction; the steeper the line, the greater the rate of reaction.
• What happens to the line on a graph when a reaction is fast?

  In fast reactions, the line becomes horizontal and finishes sooner than slower reactions.
• How can the rate of a chemical reaction be measured in higher education?

  The rate of a chemical reaction can also be measured in Mol s$^{-1}$.
• What is the relationship between the frequency of successful collisions and the reaction rate?

  The greater the frequency of successful collisions, the greater the reaction rate.
• What does the concentration of a solution indicate?

  The concentration indicates how much of a substance is dissolved in water.
• How does increasing the concentration of a reacting solution affect the reaction rate?

  Increasing the concentration increases the number of particles present, leading to more collisions.
• What happens to the frequency of collisions when the pressure of a reacting gas is increased?

  The frequency of collisions increases as the reactant particles become more crowded.
• What is meant by a successful collision in a chemical reaction?

  A successful collision is one that has enough energy for a reaction to occur.
• What does the mean energy of the particles refer to in a reaction?

  The mean energy refers to the average energy of the particles in the system.
• How can the rates of two or more reactions be compared?

  The rates can be compared using a graph of mass or volume of product formed against time.
• What do the curved red and green lines on a reaction graph represent?

  The curved lines represent the reaction data for two different reactions over time.
• What does the steepness of a tangent on a reaction graph indicate?

  The steeper the tangent, the faster the reaction is occurring.
• What happens to the steepness of the tangent as the reaction progresses?

  The steepness of the tangent decreases, indicating that the reaction is slowing down.
• How do you calculate the rate of reaction from the gradient of a tangent?

  The rate of reaction is calculated using the equation: $rate~of~reaction =$$\frac{change~in~mass~or~volume~of~product}{change~in~time}$.
• What is the rate of reaction if the change in volume of product is 60 cm³ over 5 seconds?

  The rate of reaction is $12 \text{ cm}^3/\text{s}$.
• What factors affect the rate of reaction?

  • Frequency of successful collisions
  • Concentration of reacting solutions
  • Pressure of reacting gases
  • Surface area to volume ratio
  • Temperature
  • Presence of catalysts
• What are the key concepts related to rates of reaction?

  • Successful collisions lead to reactions
  • Concentration increases collision frequency
  • Pressure increases collision frequency in gases
  • Tangents on graphs indicate reaction rates
  • Rate of reaction can be calculated from gradients
• What is a catalyst?


  A substance that changes the rate of a chemical reaction without being changed by the reaction itself.
• How does a catalyst affect the rate of a reaction?

  A catalyst increases the rate of a reaction by providing an alternative reaction pathway with lower activation energy.
• What is activation energy?

  The minimum amount of energy that colliding particles must have for them to react.
• What happens to the frequency of successful collisions when a catalyst is used?

  The frequency of successful collisions increases because more particles have energy greater than the activation energy.
• How do catalysts appear in the overall chemical equation for a reaction?

  Catalysts do not appear in the overall chemical equation for a reaction.
• What is the role of enzymes in biological reactions?

  • Enzymes are proteins that catalyse or speed up chemical reactions.
  • They are specific to particular reactions.
  • They lower the activation energy required for reactions.
• What is a reaction profile?


  A chart showing how the energy of reactants and products changes during a reaction.
• What does a reaction profile illustrate regarding energy?

  A reaction profile illustrates how the energy of the reactants and products changes during a reaction.
• What is the significance of the activation energy in a reaction profile?

  The activation energy is significant because it determines the minimum energy required for a reaction to occur.
• How much mass of a catalyst is needed to increase the rate of a reaction?

  Only a very small mass of catalyst is needed to increase the rate of a reaction.
• Why might not all reactions have suitable catalysts?

  Not all reactions have suitable catalysts because different substances catalyse different reactions.