rate and extent of chemical change

• Limiting reactant

  reactant that is completely used up in a reaction
• What is required for a reaction to take place?

  Particles must collide with sufficient energy
• What factors affect the rate of reaction?

  • Collision theory
  • Catalysts
  • Temperature
  • Concentration of reactants
  • Surface area of reactants
  • Pressure of reacting gases
• How do catalysts affect the rate of reaction?

  They provide an alternate reaction pathway
• What is the role of enzymes in reactions?

  Enzymes are biological catalysts
• What does activation energy refer to?

  Minimum energy required for a reaction
• How does collision frequency affect reaction rate?

  More collisions lead to faster reactions
• How does concentration affect the rate of reaction?

  Higher concentration increases particle number
• What happens when pressure of reacting gases increases?

  Particles occupy a smaller space
• How does temperature influence particle speed?

  Higher temperature increases particle speed
• What is the effect of increasing surface area on reactions?

  More exposed reactants increase reaction rate
• How can you increase the surface area of a reactant?

  Use a powdered form of the reactant
• What is the formula for rate of reaction?

  Rate = Amount used/Time
• What are the units for rate of reaction?

  g/s or cm³/s or mol/s
• How can you interpret graphs of reaction rates?

  • Look for the amount of reactant used/product formed over time
  • Calculate the gradient at a specific time
  • Use the tangent to measure the rate of reaction
• What does the slope of a tangent on a graph represent?

  It measures the rate of reaction
• What does the time axis represent in reaction graphs?

  Time in seconds (s)
• How do units depend on measurements in reaction graphs?

  Units depend on reactant/product measured
• What occurs at equilibrium in reversible reactions?

  The forwards and backwards reaction occur at the same rate
• What does Le Chatelier’s Principle state?

  It states that a system will counteract changes
• How is equilibrium denoted in chemical equations?

  By the symbol ⇌
• What can the products of a reversible reaction do?

  They can react to produce the original reactants
• How can the direction of a reversible reaction be changed?

  By altering the conditions of the system
• What is required for reversible reactions to reach equilibrium?

  A closed system where nothing can escape
• What factors does equilibrium depend on?

  Temperature, pressure, and concentration
• What type of energy changes occur in reversible reactions?

  Endothermic in one direction, exothermic in the other
• How much energy is transferred in each direction of a reversible reaction?

  Equal amounts of energy are transferred
• What happens if you change the conditions of a reversible reaction?

  The system will try to counteract the change
• How does a change in temperature affect equilibrium?

  Decreasing temperature shifts equilibrium in the exothermic direction
• How does a change in pressure affect equilibrium?

  Increasing pressure moves equilibrium to fewer gas molecules
• What happens when the concentration of reactants is increased?

  It increases the rate of the forwards reaction
• What does equilibrium shifting to the right indicate?

  More products are formed in the reaction
• 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 pressure affect equilibrium position?

  Increased pressure shifts equilibrium to fewer molecules
• What is the effect of temperature on equilibrium for endothermic reactions?

  Relative amount of products increases with temperature
• How does increasing reactant concentration affect reaction rate?

  It leads to more frequent successful collisions
• What is the effect of increasing pressure on gaseous reactants?

  It increases collision frequency and reaction rate