C6-The rate of Extent of chemical change

• What does a steeper line on a rate of reaction graph indicate?

  Faster rate of reaction
• How can more product be formed in a reaction?

  By using more reactant
• How can the amount of product be measured?

  In g or cm³
• How is time normally measured in reactions?

  In seconds
• What is the formula for mean rate of reaction?

  Mean rate = Amount of product / Time
• What are the common units of rate?

  cm³/s
• How can rate graphs be used to compare rates?

  By using tangents at different points
• What does a steeper tangent on a rate graph indicate?

  Faster rate of reaction at that point
• How do you calculate the mean rate over a period of time?

  Overall change in y / total time taken
• What does collision theory state about reaction rates?

  More collisions lead to faster reactions
• What happens to the reaction rate if collision frequency doubles?

  The rate doubles
• What is activation energy?

  Minimum energy needed for a reaction
• What is the role of catalysts in reactions?

  Speed up reactions without being used
• How do catalysts affect activation energy?

  They lower the activation energy
• What are enzymes?

  Biological catalysts
• How does temperature affect reaction rates?

  Higher temperature increases particle movement
• What effect does pressure have on reaction rates?

  Higher pressure increases collision frequency
• How does surface area affect reaction rates?

  More surface area leads to more collisions
• What happens to reaction rates with smaller solid pieces?

  They have a larger surface area to volume ratio
• What is required for equilibrium to be reached?

  A reversible reaction in a closed system
• What does the equilibrium expression A + B ⇌ C + D represent?

  A reversible reaction
• What happens to concentrations at equilibrium?

  They do not change
• How can changing reaction conditions affect equilibrium?

  It can change the direction of the reaction
• What is the relationship between endothermic and exothermic reactions?

  One direction is endothermic, the other exothermic
• What factors affect the rates of reaction?

  • Temperature
  • Pressure or concentration
  • Surface area
  • Presence of catalysts
• What are the characteristics of reversible reactions at equilibrium?

  • Forward and backward reactions occur at the same rate
  • Concentrations of reactants and products remain constant
  • Can be affected by changes in conditions
• What is the significance of activation energy in chemical reactions?

  • Minimum energy required for reactants to form products
  • Determines the rate of reaction
  • Lowered by catalysts