Rate & Reversible Reactions

• What is the focus of this chapter in physical chemistry?

  The factors controlling the speeds of chemical reactions and the idea of 'reversibility'
• How can reactions vary in speed?

  They can happen within fractions of a second or not at all
• What is an example of a reaction that happens very quickly?

  Explosions
• What happens to gold when exposed to air over thousands of years?

  It does not react in any way
• What are the learning objectives of this chapter?

  • Investigate effects of surface area, concentration, temperature, and catalysts on reaction rates
  • Explain these effects using particle collision theory
  • Understand catalysts and their role in reactions
  • Conduct practical experiments on reaction rates
  • Describe reversible reactions and their indicators
• What is a catalyst?

  A substance that increases the rate of a reaction but is chemically unchanged at the end
• How does a catalyst work?

  By providing an alternative pathway with lower activation energy
• What practical investigations are suggested in this chapter?

  1. Effect of changing surface area of marble chips and concentration of hydrochloric acid on reaction rate
  2. Effect of different solids on catalytic decomposition of hydrogen peroxide solution
• What symbol indicates that a reaction is reversible?

  The double arrow symbol
• Give an example of a reversible reaction.

  The dehydration of hydrated copper(II) sulfate
• What is the definition of the rate of a reaction?

  The speed at which the amount of reactants decreases or products increases
• How is the rate of reaction mathematically expressed?

  $\text{rate of reaction} =$$\frac{\text{change in concentration, volume or mass}}{\text{time}}$
• What units can be used to measure the rate of reaction?

  Per second, per minute, etc.
• What does the change in concentration indicate in a reaction?

  It indicates the speed of the reaction
• What does the chapter explore regarding reactions?

  The idea of 'reversibility' in a reaction
• What is the effect of pressure of a gas on the rate of a reaction?

  It can influence the speed of the reaction