Equilibrium Expressions - Kp, Ka, Kb, Ksp, and Keq

Forward and Reverse Reactions

Cup One and Cup Two

Observation iconThe concept of equilibrium is easily observed by transferring water between two cups. In this Warm-Up activity, you will investigate equilibrium by transferring water from an almost full cup into a partially-filled cup. You will also transfer water back to the full cup from the partially-filled cup. By completing this process, you will observe the forward and reserve reaction. At the end of the investigation, both cups of water will be at equilibrium.

Equipment and Materials

  • Two equally-sized cups
  • Any beaker up to 500 mL

Procedure

  1. Fill one cup approximately 3/4ths full with water (Cup One).
  2. Leave the second cup empty (Cup Two).
  3. Using a small beaker, pour water from Cup One into Cup Two.
  4. Using the same small beaker, pour water from Cup Two into Cup One.
  5. Repeat steps three and four until both buckets are equal.

Think iconNow, consider the following questions:

    1. What processes represented the forward and reverse reactions?
    2. What does this activity show about a reaction that is at equilibrium?
    3. What would happen if you started with the water in Cup Two?