rates of reaction and extent of change

• How can rates of reactions be measured?

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

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

  Rate of reaction = 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 using 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
• What are reversible reactions?

  Reactions where products can form reactants
• How can the direction of a reversible reaction be changed?

  By changing the conditions of the reaction
• What symbol is used to represent a reversible reaction?

  ⇌
• In the Haber Process, what is the reaction represented as?

  Hydrogen + Nitrogen ⇌ Ammonia
• What happens if a reversible reaction is endothermic one way?

  It is exothermic in the opposite direction
• What is transferred in a reversible reaction?

  The same amount of energy each way
• When is equilibrium reached in a reversible reaction?

  When reactions occur at the same rate in both directions
• What does the relative amounts of substances at equilibrium depend on?

  The conditions of the reaction
• What happens if a change is made to the conditions at equilibrium?

  The system responds to counteract the change
• What occurs if the concentration of reactants is increased?

  Equilibrium shifts towards products
• What happens if the concentration of products is increased?

  Equilibrium shifts towards reactants
• How does an increase in temperature affect equilibrium?

  Equilibrium moves towards the endothermic reaction
• What happens if temperature is decreased in a reaction?

  Equilibrium moves towards the exothermic reaction
• What is the effect of temperature changes on yield in exothermic and endothermic reactions?

  • Increase in temperature:
  • Decreases yield of exothermic reaction
  • Increases yield of endothermic reaction
  • Decrease in temperature:
  • Increases yield of exothermic reaction
  • Decreases yield of endothermic reaction
• How does pressure affect gaseous reactions at equilibrium?

  Increased pressure favors fewer gas molecules
• What happens to equilibrium if pressure is increased?

  Equilibrium shifts to side with fewer moles
• What occurs if pressure is decreased in a reaction?

  Equilibrium shifts to side with more moles
• How does pressure affect yield in reactions producing different volumes of gas?

  • Larger volume of gas:
  • Increase in pressure decreases yield
  • Smaller volume of gas:
  • Increase in pressure increases yield
• Catalyst


  A substance that speeds up a chemical reaction without being consumed or altered in the process
• Catalyst and reaction yield


  Catalysts do not affect the extent of the reaction (yield), only the rate