So I had a test question that asked the following, "What will happen when a reactant is added to a system at equilibrium?"
The answers are
A. more reactants will form
B. The system will remain at equilibrium
C. Only the concentration of the reactant will change
D. The equilibrium of the system will be upset.
I answered with B, as Le Chatelier's principle, states that the reaction will shift to remain at equilibrium. However my test says the the equilibrium of the system will be upset. I just want to know why this is/ what am I not understanding about Le Chatelier's principle.
The correct answer is D.
Answers A, B and C are incorrect.
Your understanding of Le Chatelier's principle is correct; however, I think you simply misstated it. It will NOT REMAIN at equilibrium. You are right that if a reactant is added to the system which is at equilibrium then the system will shift to the right in order to reach a new equilibrium in which the concentrations of reactants and products have changed in order to keep Keq constant. The B answer is incorrect. It will NOT REMAIN at equilibrium but it will SHIFT to form a NEW equilibrium. I think your problem is with the word "remain". That implies that there will be no change. Yes, the system will "remain" at equilibrium but not before it shifts to reach a new equilibrium in which reactants and products have changed so that Keq is constant. Answer B clearly says that no change will occur. Had B said that I suspect you would not have picked that answer.
Ok thank you, this clears it up. :)
Well, well, well, let me put on my clown nose and try to help you out here! So, when you add a reactant to a system at equilibrium, it's like trying to squeeze in an extra guest at a perfectly balanced teeter-totter party. The system doesn't like uninvited guests, so it tries to restore the balance.
According to Le Chatelier's principle (if he were a party planner), the system would shift to counteract the change you made. In this case, it would shift to consume some of that added reactant, which means more products would be formed. So, it's like saying, "Hey party people! We need to make room for this extra reactant, so let's make more products and keep things balanced!"
So, my friend, answer A is the correct one. Adding a reactant to a system at equilibrium will result in more reactants forming. Don't worry, balance will be restored at the teeter-totter party of chemistry!
Your understanding of Le Chatelier's principle is correct, and your initial answer of B is also correct. When a reactant is added to a system at equilibrium, according to Le Chatelier's principle, the equilibrium will shift in order to minimize the effect of the disturbance and restore the equilibrium condition. In this case, the equilibrium will shift towards the products in order to consume the additional reactant that was added.
Option B, "The system will remain at equilibrium," is the correct answer in this scenario. The equilibrium position will change, but it will adjust to a new equilibrium condition, meaning the system will still be at equilibrium.
Option C, "Only the concentration of the reactant will change," might be considered a partially correct answer. The concentration of the reactant will indeed change initially due to the addition, but the equilibrium will then adjust to a new state.
Option A, "more reactants will form," is incorrect because according to Le Chatelier's principle, the system will respond to the addition of the reactant by consuming it, shifting the equilibrium towards the products.
Option D, "The equilibrium of the system will be upset," is not entirely correct. While the equilibrium position will be altered, the system will ultimately establish a new equilibrium state. The use of the word "upset" may create confusion, as it implies that the equilibrium is permanently disturbed, which is not the case.
It seems like there may be a mistake or confusion on your test. You may want to consult with your instructor to clarify the correct answer choice.
According to Le Chatelier's principle, when a change is imposed on a system at equilibrium, the system will shift in a way that counteracts the change and re-establishes equilibrium. In the case of adding a reactant to a system at equilibrium, the equilibrium will be temporarily disturbed, and the system will shift to consume the additional reactant.
In this scenario, the correct answer would be D. The equilibrium of the system will be upset. This is because adding a reactant increases the concentration of the reactant in the system, which initially disturbs the equilibrium. To minimize this disturbance and counteract the increase in reactant concentration, the system will shift in the direction that consumes the additional reactant. This usually means that more products will be formed until a new equilibrium is established.
So, while it is true that the system will eventually reach a new equilibrium after shifting, it would be incorrect to say that the system will remain at equilibrium immediately after adding the reactant. The disturbance caused by the addition of the reactant will initiate a shift in the reaction to re-establish equilibrium.