posted by Ben on .
The question below, i was wondering if it decrease because the N2 is on the right and so to add to left it would be too much so it gets rid of it by decreases and doing to the right? because the left side is (+) endothermic? sorry im a little confused.
if the number was negative would it make a difference?
Consider the following reaction at equilibrium:
2NH3 (g)<-> N2 (g) + 3H2 (g) ΔH° = +92.4 kJ
Le Cha^telier's principle predicts that adding N2 (g) to the system at equilibrium will result in
A) an increase in the value of the equilibrium constant
B) a decrease in the concentration of H2 (g)
C) removal of all of the H2 (g)
D) a lower partial pressure of N2
E) a decrease in the concentration of NH3 (g)
I think you are a little confused. Le Chatelier's Principle says that what we do to a rxn at equilibrium, the reaction shifts so as to undo what we did. So we added N2, the reaction shifts to try to get rid of the N2; therefore, it shifts to the left. That means NH3 will increase, H2 will decrease, N2 is the agent causing the "problem" so we don't worry about it too much. In reality, and we can calculate to what extent it occurs, N2 gets larger (because we've added to it), the reaction shifts and SOME of the excess is used up but the original amount we had PLUS the amount we added still will be more than we started with but less than the sum of the two. From this analysis, you should pick B as the correct answer.
A. The equilibrium constant changes ONLY with a change in temperature.
C. No, removal of some of the hydrogen but not ALL of it. We hardly ever get ALL of anything.
D. If we ADD N2, the partial pressure will increase.
E. A shift to the left means more NH3, not less NH3.
A shift to the left also means that some heat is generated since it is an endothermic reaction AND we are shifting to the heat side.