K in endo and exo when temp. decreases

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Cristian Cortes 1L
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K in endo and exo when temp. decreases

Postby Cristian Cortes 1L » Wed Jan 13, 2021 12:18 am

When temp increases K goes up for endo and K goes down for exo reaction. WHat occurs, if possible, when temp decreases.

Victor Li 2A
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Re: K in endo and exo when temp. decreases

Postby Victor Li 2A » Wed Jan 13, 2021 12:37 am

According to Le Chatelier's principle, chemical reactions adjust so as to minimize the effect of changes. Therefore, I believe decreasing the temperature will increase the K value (more products) for an exothermic reaction and decrease the K value for an endothermic reaction. Please correct me if I am wrong.

Uyenvy Nguyen 1D
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Re: K in endo and exo when temp. decreases

Postby Uyenvy Nguyen 1D » Wed Jan 13, 2021 1:52 am

I believe the above reply is correct. Decreasing temperature would increase the K value for exothermic reactions decrease the K value for endothermic reactions.

Aaina 2D
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Re: K in endo and exo when temp. decreases

Postby Aaina 2D » Wed Jan 13, 2021 8:58 am

Victor Li 2A wrote:According to Le Chatelier's principle, chemical reactions adjust so as to minimize the effect of changes. Therefore, I believe decreasing the temperature will increase the K value (more products) for an exothermic reaction and decrease the K value for an endothermic reaction. Please correct me if I am wrong.


This is correct. In an exothermic reaction, heat is being released. When temperature decreases, you're decreasing heat, and so the reaction will move in the forward direction, thereby increasing the value of K. Similarly, if the reaction is endothermic, heat is needed for the reaction to move forward, and if you decrease temperature, the reaction will move in the reverse direction, thereby decreasing the value of K.

Hope this helps!

Gina Spagarino 3G
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Re: K in endo and exo when temp. decreases

Postby Gina Spagarino 3G » Wed Jan 13, 2021 10:19 am

On the SAPLING with the questions about temp changes and k changes, I found it helpful to think about which direction the reaction will shift based on whether the forward or reverse was endothermic, then whether K would have to increase or decrease to cause a shift in this direction when compared to Q... so by that logic a decrease in temperature will increase the K value of an exothermic reaction because the reaction shifts to products, so Q<K, meaning K is larger than it was before the temp decrease.

Sreeram Kurada 3H
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Re: K in endo and exo when temp. decreases

Postby Sreeram Kurada 3H » Wed Jan 13, 2021 10:52 am

This difference is due to the place where heat is being added in the reaction. Because heat is in the reactants side for endo, when decreased reactants are favored. On the other hand, since heat is on the product's side for exo, when decreased products are favored.

Libby Dillon - 1A
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Re: K in endo and exo when temp. decreases

Postby Libby Dillon - 1A » Wed Jan 13, 2021 12:09 pm

An exothermic reaction means heat is being released. During a step - up session the UA described heat as one of the products of the reaction which I found helpful. So, as more heat is released and the temperature decreases, there are essentially more "products", so the K value will increase.

Andrew Yoon 3L
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Re: K in endo and exo when temp. decreases

Postby Andrew Yoon 3L » Fri Jan 15, 2021 8:41 pm

When decreasing the temp, the k value will increase. This is an exothermic reaction. You can also see if the reaction is exothermic if delta H is negative.

Rob Tsai 2F
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Re: K in endo and exo when temp. decreases

Postby Rob Tsai 2F » Sat Jan 16, 2021 4:15 am

I'm fairly certain you are correct. Endothermic reactions require heat to react, so if the temperature decreases, less products would be made, and therefore K would decrease. I'm not entirely sure about the logic of exothermic reactions, but the decrease in temperature probably increases products being made, so K would increase.

Emma_Barrall_3J
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Re: K in endo and exo when temp. decreases

Postby Emma_Barrall_3J » Sat Jan 16, 2021 10:19 am

It is important to remember that in equilibrium reactions, if the forward reaction is endothermic, the reverse is exothermic, and vice versa. For this reason, if temperature decreases: an endothermic reaction will shift left and an exothermic reaction will shift right.

Xavier Herrera 3H
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Re: K in endo and exo when temp. decreases

Postby Xavier Herrera 3H » Sat Jan 16, 2021 11:33 am

I was also a little confused about this on Sapling. From what I understand, if temperature is decreased in an exothermic reaction, more products would be formed since heat is a product. This will increase the value of K, resulting in Q < K. Similarly, if temperature is decreased in an endothermic reaction, more reactants would have to be formed since heat is a reactant. This will decrease the K value, causing Q to be greater than K.

Joey_Okumura_1E
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Re: K in endo and exo when temp. decreases

Postby Joey_Okumura_1E » Sat Jan 16, 2021 11:51 am

I find it helpful to think about heat as a reactant or product. In an endothermic reaction, heat is being absorbed and is a reactant. Therefore, adding heat will cause the equilibrium to shift towards the products. In an exothermic reaction, heat is being released and is a product. Therefore, adding heat will cause the equilibrium to shift towards the reactants.


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