Prelab Assignment: Chemical Equilibrium and Le Chatelier's Principle
1. Consider the reversible reaction: A + B ⇌ C + D
a. What happens to the forward and reverse reaction rates when equilibrium is achieved?
b. What happens to the reactant (A and B) and product (C and D) concentrations when equilibrium is achieved?
2. Le Chatelier's Principle states that if a stress is applied to a reversible reaction at equilibrium, the reaction will undergo a shift in order to re-establish its equilibrium. Consider the following exothermic reversible reaction at equilibrium:
2 A ⇌ B + C
In which direction (left or right) would the following stresses cause the system to shift?
a. decrease the concentration of A
b. increase the concentration of B
c. lower the temperature
3. In this lab you will explore the effect of Le Chatelier's Principle on several chemical systems at equilibrium. These are supplied on page 2 of the Theory Section. Consider the third system you will study: the Aqueous Ammonia Solution.
a. Write the balanced equation for this reversible reaction.
b. Suppose you added some excess ammonium ions to this system at equilibrium.
-- In which direction would a shift occur?
-- What color change might you expect to observe?
4. List all the equipment you will use in this lab.