Rates Of Reaction

• What is the Rate of Reaction?

  A measure of how fast a reaction happens
• How can the rate of a reaction be observed?

  By measuring reactants used or products formed
• How do you calculate the average rate of reaction?

  $\text{Average Rate} =$$\frac{\text{amount of reactant used}}{\text{time}}$
• What are three methods to measure reaction rates?

  • Precipitation
  • Change in mass (gas produced)
  • Volume of gas given off
• What does the precipitation method measure?

  Time taken for a mark to disappear
• What is a limitation of the precipitation method?

  The result is subjective and varies by observer
• How is the change in mass method used?

  By measuring mass loss as gas is released
• What indicates that a reaction has finished in the change in mass method?

  When the mass reading stops changing
• What is the purpose of using a gas syringe in measuring reaction rates?

  To measure the volume of gas produced
• What should you ensure when using a gas syringe?

  Use the right size syringe for the reaction
• What are the three methods to follow reaction rates mentioned?

  1. Precipitation
  2. Change in mass
  3. Volume of gas given off
• What happens to the reaction rate when temperature increases?

  The reaction rate increases
• Why does increasing temperature increase reaction rate?

  Particles move faster and collide more often
• How can surface area affect the rate of reaction?

  Smaller particles increase surface area for collisions
• What is the relationship between concentration and reaction rate?

  Higher concentration increases the reaction rate
• How does breaking a solid reactant into smaller pieces affect the reaction rate?

  It increases the surface area and collision frequency
• What is a catalyst?

  A substance that increases reaction rate
• How does a catalyst affect activation energy?

  It decreases the activation energy needed
• Why is a catalyst not used up in a reaction?

  It remains chemically unchanged after the reaction
• What factors affect the rate of reaction according to collision theory?

  • Collision frequency of particles
  • Number of successful collisions
  • Activation energy needed for reactions
• What is the significance of the gradient in a reaction rate graph?

  Steeper gradients indicate faster reaction rates
• How do you find the gradient of a curve on a graph?

  By drawing a tangent at the point of interest
• What is the formula for calculating the gradient?

  $\text{gradient} =$$\frac{\text{change in y}}{\text{change in x}}$
• What does a flat line on a reaction rate graph indicate?

  No more gas is being produced
• How do you determine the rate of reaction at a specific time from a graph?

  By calculating the gradient of the tangent
• What is the effect of increasing pressure on gas reactions?

  It increases the reaction rate
• Why do catalysts not change the products of a reaction?

  They provide an alternative pathway without altering products
• What happens to the reaction rate when a catalyst is added?

  The reaction rate increases without changing reactants
• What are the key points about catalysts?

  • Increase reaction rate
  • Not chemically changed or used up
  • Do not change reaction products
  • Lower activation energy
• What is a faster reaction dependent on?

  Collisions between reactant particles
• Why doesn't every collision result in a reaction?

  Not all collisions have sufficient energy
• What are the two factors affecting the rate of reaction?

  Frequency and energy of collisions
• How does breaking a solid reactant into smaller pieces affect reaction rate?

  Increases surface area for more collisions
• What is a catalyst?

  A substance that increases reaction rate
• How does a catalyst affect the products of a reaction?

  It doesn't change the products of the reaction
• Why is only a small amount of catalyst needed?

  It isn't consumed in the reaction
• What do catalysts do to activation energy?

  They decrease the activation energy needed
• What are enzymes?

  Biological catalysts that speed up reactions
• What reactions do enzymes catalyse?

  Respiration, photosynthesis, and protein synthesis
• What is an exothermic reaction?

  A reaction that releases energy to surroundings