K Favors Products or Reactants

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Amanda Bueno-Kling
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K Favors Products or Reactants

Postby Amanda Bueno-Kling » Sun Jan 10, 2021 9:51 pm

How can we tell if the products or reactants are favored using K? I know a large K value shows that the products are favored, but what qualifies as large or small K values?

Marc Lubman 3B
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Re: K Favors Products or Reactants

Postby Marc Lubman 3B » Sun Jan 10, 2021 9:54 pm

If K is greater than 1, then products are favored, and if K is less than 1, reactants are favored. This is because K=[products]/[reactants], so a value greater than one means the concentration of products is greater than that of reactants. So I guess you could say that a "large" K value is just greater than 1, and a "small" one is less than 1.

Ethan Laureano 3H
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Re: K Favors Products or Reactants

Postby Ethan Laureano 3H » Sun Jan 10, 2021 9:54 pm

Large K values are anything above 10^3 and small K values are anything below 10^-3

Rich Luong 1D
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Re: K Favors Products or Reactants

Postby Rich Luong 1D » Sun Jan 10, 2021 9:55 pm

Typically, what counts as a large k value is >10^3 and what counts as a small k value is <10^-3. However, essentially I use 1 as a sort of threshold for k. Whenever k is lower than 1, the reactants are favored. Whenever k is higher than 1, the products are favored. I hope this helps!

Gabby Magat 3F
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Re: K Favors Products or Reactants

Postby Gabby Magat 3F » Sun Jan 10, 2021 10:00 pm

Rich Luong 1D wrote:Typically, what counts as a large k value is >10^3 and what counts as a small k value is <10^-3. However, essentially I use 1 as a sort of threshold for k. Whenever k is lower than 1, the reactants are favored. Whenever k is higher than 1, the products are favored. I hope this helps!


This is really helpful! I think 10^3 and 10^-3 are commonly used to reference when determining if K is large or small (if P or R is strongly favored). Since K is still a ratio, K = 1 would mean that the concentrations of reactants and products are equal and the forward/reverse rates are the same.

Nick Saeedi 1I
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Re: K Favors Products or Reactants

Postby Nick Saeedi 1I » Sun Jan 10, 2021 10:02 pm

Large is greater than 10^3 and small is less than 10^-3

Amanda Bueno-Kling
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Re: K Favors Products or Reactants

Postby Amanda Bueno-Kling » Sun Jan 10, 2021 10:04 pm

Gabby Magat 3F wrote:
Rich Luong 1D wrote:Typically, what counts as a large k value is >10^3 and what counts as a small k value is <10^-3. However, essentially I use 1 as a sort of threshold for k. Whenever k is lower than 1, the reactants are favored. Whenever k is higher than 1, the products are favored. I hope this helps!


This is really helpful! I think 10^3 and 10^-3 are commonly used to reference when determining if K is large or small (if P or R is strongly favored). Since K is still a ratio, K = 1 would mean that the concentrations of reactants and products are equal and the forward/reverse rates are the same.


Thank you all for explaining! So if K=1, does that mean that the reaction is in equilibrium and the concentrations of the products and reactants are not changing? So K being less than one or greater than one means one side is favored, but K being equal to one means neither side is favored?

Mansi Solanki 3A
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Re: K Favors Products or Reactants

Postby Mansi Solanki 3A » Sun Jan 10, 2021 10:10 pm

During lecture, I think that Dr. Lavelle said that for this course any K value that is less than 10^-3 will be considered small while any K value that is greater than 10^3 will be considered large. These values are meant to show whether one side is actually significantly more favored than the other.

DominicMalilay 1F
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Re: K Favors Products or Reactants

Postby DominicMalilay 1F » Sun Jan 10, 2021 10:17 pm

The large k value is usually for 10^3 while small k value is 10^-3!

Marc Lubman 3B
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Re: K Favors Products or Reactants

Postby Marc Lubman 3B » Sun Jan 10, 2021 10:29 pm

Amanda Bueno-Kling 2L wrote:
Gabby Magat 3F wrote:
Rich Luong 1D wrote:Typically, what counts as a large k value is >10^3 and what counts as a small k value is <10^-3. However, essentially I use 1 as a sort of threshold for k. Whenever k is lower than 1, the reactants are favored. Whenever k is higher than 1, the products are favored. I hope this helps!


This is really helpful! I think 10^3 and 10^-3 are commonly used to reference when determining if K is large or small (if P or R is strongly favored). Since K is still a ratio, K = 1 would mean that the concentrations of reactants and products are equal and the forward/reverse rates are the same.


Thank you all for explaining! So if K=1, does that mean that the reaction is in equilibrium and the concentrations of the products and reactants are not changing? So K being less than one or greater than one means one side is favored, but K being equal to one means neither side is favored?


Though K can be 1 at equilibrium, K not being 1 does not necessarily mean that the reaction is not at equilibrium and that concentrations are unchanging. A K of any value describes the equilibrium state, and concentrations can still be unchanging even if K=!1. But you're totally right that if K is equal to 1 then neither products nor reactants are favored at equilibrium—their concentrations (products as a whole and reactants as a whole, not necessarily individual reactants or products) are equal.

Dane_Beasley_1E
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Re: K Favors Products or Reactants

Postby Dane_Beasley_1E » Sun Jan 10, 2021 10:32 pm

A large K would constitute as anything above 10^3 and a small K would be anything lower than 10^3.

Katy Austin 1K
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Re: K Favors Products or Reactants

Postby Katy Austin 1K » Sun Jan 10, 2021 10:56 pm

If K > 10^3, equilibrium strongly favors P and if K<10^-3, equilibrium strongly favors R. Intermediate values (10^-3<K< 10^3) of K don't strongly favor either products or reactants but do slightly favor them.

David Liu 1E
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Re: K Favors Products or Reactants

Postby David Liu 1E » Sun Jan 10, 2021 10:58 pm

A large k value is anything over 10^3 and a small value would be anything lower than 10^-3!

Geethika Janga 1L
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Re: K Favors Products or Reactants

Postby Geethika Janga 1L » Sun Jan 10, 2021 10:59 pm

If the K value is small (K<10^-3) then the equilibrium sits to the left and if the K is large (K>10^3) then the equilibrium sits to the right.

Justin Zhang_1A
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Re: K Favors Products or Reactants

Postby Justin Zhang_1A » Sun Jan 10, 2021 11:00 pm

A large K value is anything over 10^3 while a small K value is less than 10^-3, but if a K value is larger than 1, the products are favored, and if the K value is less than 1, the reactants are favored.

Jared Limqueco 3E
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Re: K Favors Products or Reactants

Postby Jared Limqueco 3E » Sun Jan 10, 2021 11:03 pm

Large K is above 10^3, and a small K is below 10^3.

Uyen Trinh 3C
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Re: K Favors Products or Reactants

Postby Uyen Trinh 3C » Sun Jan 10, 2021 11:06 pm

I just wanted to add that when K is any value in between the chemistry-defined cutoffs of 103 or 10-3, neither the reactants nor the products are favored. So we do not have a strong statement on whether the equilibrium favors the right or the left.

Joanna Huang
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Re: K Favors Products or Reactants

Postby Joanna Huang » Sun Jan 10, 2021 11:08 pm

K>1 = products favored, since K=[products]/[reactants]. By the same logic, K<1 = reactants favored

Brandon McClelland3L
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Re: K Favors Products or Reactants

Postby Brandon McClelland3L » Sun Jan 10, 2021 11:13 pm

In this case, large would be >1 and small would be <1. At 1, neither would be favored.

TiffanyBrownfield 2I
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Re: K Favors Products or Reactants

Postby TiffanyBrownfield 2I » Sun Jan 10, 2021 11:28 pm

Using the equation Kc = [P]/[R], we can determine whether the products or reactants are favored. If the numerator (concentration of products) is greater than the denominator (concentration of reactants), the value of K will be greater than 1. If it were the other way around and the denominator were greater, that would mean the concentration of reactants is greater and K would be less than 1.

Samir 3I
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Re: K Favors Products or Reactants

Postby Samir 3I » Sun Jan 10, 2021 11:42 pm

It's important to use the rules that K<10^-3 is a small K and K>10^3 is a large K value because these are the values where either products or reactants are STRONGLY FAVORED, whereas the intermediate values between 10^-3 and 10^3 (besides K=1) are values where neither products nor reactants are strongly favored.


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