posted by Abby on .
Consider the following reaction that has reached equilibrium:
NH3 (aq) + C2H4O2 (aq) ! NH4+ (aq) + C2H3O2- (aq) ∆H = -102.1 kJ
a. What will happen to the concentration of NH4+ (aq) if the temperature is raised?
b. What will happen to the concentration of NH4+ (aq) if the concentration of NH3 is lowered?
Two questions on Le Chatelier's Principle. You can read about the Principle in texts but boiled down to every day language here it what it says. Pay attention.
For a system at equilibrium, it will try to undo what we do to it.
Therefore, let me re-write the equation as
NH3 (aq) + C2H4O2 (aq) ! NH4+ (aq) + C2H3O2- (aq) ∆H = -102.1 kJ to the following.
NH3 (aq) + C2H4O2 (aq) ! NH4+ (aq) + C2H3O2- (aq) + heat
Now, if we add heat, the reaction will shift so as to undo it; therefore, the reaction will move to use up the heat. That means it moves to the left (there are always only three answers to these problems. 1. shift to the right 2. shift to the left 3. no change.)
2. If we remove NH3 from the reaction, it will shift to produce more NH3 and the only way it can do that is to shift to the left. Shifting to the left means NH4^+ is used so (NH4^+) will be lowered.