Topic 6: The Rate and Extent of Chemical Change

• What is activation energy?

  The minimum energy for particles to react
• How do catalysts affect the rate of reaction?

  They provide a pathway with lower activation energy
• What does collision theory state?

  Reactions occur when particles collide with energy
• What happens to product formation when reactant concentration increases?

  More products are formed until equilibrium is reached
• How does decreasing product concentration affect equilibrium?

  More reactants will react until equilibrium is reached
• What is the effect of increasing pressure on equilibrium?

  Equilibrium shifts to the side with fewer molecules
• What happens to equilibrium when pressure is decreased?

  Equilibrium shifts to the side with more molecules
• How does increasing temperature affect an endothermic reaction at equilibrium?

  Relative amount of products increases
• What is the effect of increasing temperature on an exothermic reaction at equilibrium?

  Relative amount of products decreases
• How does increasing reactant concentration affect reaction rate?

  It increases the rate of successful collisions
• What is the effect of increasing pressure on gaseous reactants?

  It increases the rate of successful collisions
• How does increasing surface area affect reaction rate?

  It increases the frequency of successful collisions
• What happens to particles when temperature is increased?

  Particles gain kinetic energy and move faster
• Why does the rate of reaction increase with temperature?

  Faster particles collide more often with energy
• What is equilibrium in a reversible reaction?

  Forward and reverse reactions occur at the same rate
• What does Le Chatelier’s Principle state?

  Equilibrium shifts to counteract changes in conditions
• How is the rate of reaction measured?

  Amount of product formed or reactant used over time
• What are the units of rate of reaction?

  g/s, cm³/s, or mol/s
• What is a reversible reaction?

  Products can react to form original reactants
• What are the effects of changing concentration, pressure, and temperature on equilibrium?

  • Increasing reactant concentration: more products formed
  • Decreasing product concentration: more reactants react
  • Increasing pressure: shifts to fewer molecules
  • Decreasing pressure: shifts to more molecules
  • Increasing temperature (endothermic): more products
  • Increasing temperature (exothermic): fewer products
• What factors affect the rate of reaction?

  • Concentration: higher concentration increases collisions
  • Pressure: higher pressure increases collisions
  • Surface area: larger area increases collisions
  • Temperature: higher temperature increases kinetic energy and collisions
• How can rates of reactions be measured?

  By amount of product used or formed
• What is the formula for the rate of reaction using reactants?

  Rate = amount of reactant used / time
• What is the formula for the rate of reaction using products?

  Rate = amount of product formed / time
• How can the quantity of reactant or product be measured?

  By mass in grams or volume in cm³
• What are the units of rate of reaction?

  g/s or cm³/s
• How can quantity of reactants be expressed in terms of moles?

  Using moles instead of mass or volume
• What are the units for rate of reaction in moles?

  mol/s
• How can the rate of reaction be found graphically?

  By drawing tangents to curves and calculating slopes
• What does the gradient of a tangent represent in reaction rate graphs?

  It measures the rate of reaction at a specific time
• What factors affect the rates of chemical reactions?

  • Concentration
  • Pressure
  • Surface area
  • Temperature
  • Catalysts
• What is collision theory in relation to chemical reactions?

  Reactions occur when particles collide with sufficient energy
• What is activation energy?

  The minimum energy required for particles to react
• How does increasing concentration affect reaction rates?

  It increases the frequency of collisions
• How does increasing temperature affect reaction rates?

  It increases collision frequency and energy
• What are catalysts?

  Substances that speed up reactions without being used
• How do enzymes function in biological systems?

  They act as catalysts in biochemical reactions
• Are catalysts included in the reaction equation?

  No, they are not included
• How do catalysts affect activation energy?

  They decrease activation energy required for reactions
• What do catalysts provide for chemical reactions?

  A different pathway with lower activation energy