06- the rate and extent of chemical change

• How is the rate of reaction calculated?

  Rate of reaction = amount / time
• What is the formula for rate of reaction in moles?

  Rate of reaction (mol/s) = moles / time
• Name three common ways of measuring the rate of reaction.

  Loss in mass, volume of gas, time for opacity
• What are the various units for rate of reaction?

  g/s, cm³/s, mol/s
• Describe measuring the rate by monitoring mass loss.

  • Place reaction flask on a balance
  • Record mass decrease over time intervals
  • Plot graph of mass vs time
• Describe measuring the rate by monitoring the volume of gas.

  • Connect gas syringe to reaction flask
  • Measure gas volume formed over time intervals
  • Plot graph of volume vs time
• How to find the rate of reaction at time t from a graph?

  • Pick point at time t
  • Find tangent to curve at this point
  • Gradient of tangent indicates reaction rate
• Describe measuring the rate by monitoring the disappearance of a cross.

  • Mark a cross on paper
  • Place reaction flask on the cross
  • Measure time until cross is concealed
• State five factors affecting the rate of a chemical reaction.

  Concentration, pressure, surface area, temperature, catalysts
• What is the collision theory?

  Reactions occur when particles collide with sufficient energy
• How does increasing concentration affect the rate of reaction?

  Higher concentration leads to more frequent collisions
• How does increasing temperature affect the rate of reaction?

  Higher temperature increases kinetic energy and collision frequency
• How does increasing pressure of a gas affect the rate of reaction?

  Increased pressure raises collision frequency among gas molecules
• What is a catalyst?

  A catalyst changes reaction rate without being used up
• How does a catalyst affect the reaction profile?

  A catalyst lowers the activation energy of the reaction
• How does increasing surface area affect the rate of reaction?

  Smaller pieces increase surface area and collision frequency
• What is an enzyme?

  An enzyme is a biological catalyst
• When is dynamic equilibrium reached?

  When forward and reverse reactions occur at the same rate
• How does changing the concentration of reactants and products affect equilibrium?

  Changes shift equilibrium until a new balance is reached
• What is Le Chatelier’s Principle?

  System responds to counteract changes and restore equilibrium
• What is a reversible reaction?

  Products can react backwards to form original reactants
• How does changing pressure affect the position of equilibrium?

  Increased pressure shifts equilibrium to fewer gas molecules
• How does changing temperature affect the position of equilibrium?

  Increased temperature favors endothermic reactions
• What is the effect of a catalyst on the position of equilibrium?

  A catalyst has no effect on equilibrium position