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Posted: Wed Jan 09, 2019 10:17 pm
I remember learning about things that "shift" equilibrium in high school, but Dr. Lavelle said to avoid that word. Could someone explain to me what he means by equilibrium "sitting" to the left and not "shifting" to the left?
Posted: Wed Jan 09, 2019 10:20 pm
If you refer to a system "shifting" it is implying that it is no longer at equilibrium.
Posted: Wed Jan 09, 2019 10:21 pm
"Sitting" to the left simply means the reaction is favored towards the reaction side, or the left side of the equation.
Posted: Wed Jan 09, 2019 10:24 pm
I like to imagine a number line, with 0 being equilibrium, negative numbers being reactants, and positive numbers being products. If you added more reactants to the system, you suddenly have more reactants than equilibrium, so you're sitting to the left of 0 (equilibrium). To move back to 0, you need to move to the right (from negative to 0), which means more products are being formed and the forward reaction is favored. So where you are on the line in relation to equilibrium helps you find out which reaction is favored. Hope this helps! :)
Posted: Wed Jan 09, 2019 10:40 pm
I think he meant to differentiate between "sitting" and "shifting". When equilibrium 'sits' to the right, reactants are favored, and when it 'sits' on the left, products are favored. On the other hand, "shifting" means that the reaction is moving towards equilibrium (which all chemical reactions do). In order to achieve equilibrium and depending on the type of reaction and how much of the reactants or products there are, if there are too many reactants (so that the ratio is off), the reaction will shift to the products side, and vice versa.
Posted: Wed Jan 09, 2019 10:56 pm
Dr. Lavelle told us to use the phrases "favor the products" and "favor the reactants."
Posted: Sat Jan 12, 2019 5:52 pm
Consider "sitting" as describing which side (reactants or products) the reaction favors, and "shifting" only when referring to a change.
Posted: Mon Jan 14, 2019 2:52 pm
If a reaction "sits" toward the product side, it implies that K is large.
If a reaction "sits" toward the reactant side, it implies that K is small (less than 1).
The word "shift" is used when the reaction is not at equilibrium or when equilibrium is disturbed (Le Chatlier's principle) and you want to see which direction the reaction favors after.
Posted: Mon Jan 14, 2019 3:21 pm
What Dr. Lavelle means when a reaction at equilibrium is sitting left, he means that there are more reactants at equilibrium than products so the K is very small. When a reaction is sitting right, there are more products at equilibrium than reactants so the K is very big. The direction the reaction at equilibrium is sitting means what reaction is favored: the forward or reverse.
Posted: Mon Jan 14, 2019 7:15 pm
Shifting refers to the direction in which a the reaction favors, more of the product or reactant.
Posted: Tue Jan 15, 2019 10:15 pm
Shifting can be a confusing term because it can give the impression that the reaction is moving. In fact, "shifting," "lie to," and "favored" all mean the same thing. This term either denotes that a reaction favors the reactants or products depending on a condition. The equilibrium constant does not change in these circumstances unless temperature is changed.
Posted: Wed Jan 16, 2019 2:20 pm
I too recall him saying 'shifting' is used more when referring when the reaction is not at equilibrium and prefers the term 'leans towards right/left' to indicate if it favors products or reactants.
Posted: Thu Jan 17, 2019 2:12 pm
"sitting" means the reaction favors one side, whether it's reactants or products
Posted: Thu Jan 17, 2019 9:03 pm
During the lecture on January 8th, Dr. Lavelle referenced other terms for shifting or lying, stating that the preferred term is sitting when analyzing the size of the value K.
Posted: Sat Jan 19, 2019 9:15 pm
Sitting to the left just means that the reactants are being favored over the products. Thus, if it is shifting left, the reactants are being favored to reach equilibrium.
Posted: Sat Jan 19, 2019 9:35 pm
He avoided using the word "shift" because some students confuse the reaction favoring foward or reverse directions of reaction as actually changing the K constant; sitting just refers to the reaction no longer being at equilibrium and that the reaction will proceed in that specific direction to restore the equilibrium.