Q and K

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Jasmin Argueta 1K
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Q and K

Postby Jasmin Argueta 1K » Thu Jan 10, 2019 9:47 pm

I know a few people already asked, but I am still a bit confused. I know Q is the reaction quotient and K is the equilibrium constant. Although, I don't understand why they are calculated the same way how will K ever be greater or Q ever be greater. Because in our notes it states a smaller q means you have more reactants , and a larger q means you have more products

Parth Mungra
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Re: Q and K

Postby Parth Mungra » Thu Jan 10, 2019 9:49 pm

It was meant to be in comparison to K. A Q<K means more products, and Q>K means more reactants. Q can be calculated at any time during a reaction.

Mindy Kim 4C
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Re: Q and K

Postby Mindy Kim 4C » Thu Jan 10, 2019 10:18 pm

Also keep in mind that when you are calculating Q, the reaction composition/mixture given in the problem is not at equilibrium. Therefore, Q will be greater or smaller than K depending on how much more reactants/products there are in the given reaction mixture.

Dakota_Campbell_1C
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Re: Q and K

Postby Dakota_Campbell_1C » Thu Jan 10, 2019 10:20 pm

In regards to calculating K, the values that are inputted into the equation are concentrations or partial pressures whereas when Calculating Q the values inputted are initial values not equilibrium values.

Vicky Lu 1L
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Re: Q and K

Postby Vicky Lu 1L » Thu Jan 10, 2019 10:26 pm

The difference between Q and K is that Q is an expression that can be used to describe the composition of the reaction mixture at any time of the reaction. And also between Q and K, the reaction quotient Q at equilibrium is equal to the equilibrium constant K.

Emilia z
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Re: Q and K

Postby Emilia z » Fri Jan 11, 2019 2:39 pm

Usually if you are solving a problem involving both K and Q, you will be given a value for K for which you will compare the value you get for Q to. This is because the chemical equation you are given is not necessarily at equilibrium, and to find this out you compare your K and Q values (if they are equal, your system is at equilibrium).

Anjali_Kumar1F
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Re: Q and K

Postby Anjali_Kumar1F » Fri Jan 11, 2019 4:09 pm

Can someone help me with 11.33 from the 6th edition tb. I keep on getting 69.4 instead of 6.9.

Raj_Bains_2C
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Re: Q and K

Postby Raj_Bains_2C » Fri Jan 11, 2019 4:11 pm

K is when the reaction is at equilibrium and Q is the current state of the reaction. If Q = K, the reaction is at equilibrium and if Q does not equal K, the reaction is not at equilibrium.

KHuang1L
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Re: Q and K

Postby KHuang1L » Fri Jan 11, 2019 4:32 pm

You calculate K by using the concentration of the reactants and products when the reaction is in equilibrium. You calculate Q by using the concentration of the reactants and products when the reaction is or is not in equilibrium. That is why Q is sometimes greater or smaller than K.

Anita Wong 1H
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Re: Q and K

Postby Anita Wong 1H » Fri Jan 11, 2019 4:39 pm

When comparing the two, usually you’ll be given K and you’ll have to calculate Q.

amogha_koka3I
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Re: Q and K

Postby amogha_koka3I » Fri Jan 11, 2019 7:47 pm

Should we specify Qc And Qp just like we differentiate between Kc and Kp?

Xinyi Zeng 4C
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Re: Q and K

Postby Xinyi Zeng 4C » Fri Jan 11, 2019 8:49 pm

amogha_koka3I wrote:Should we specify Qc And Qp just like we differentiate between Kc and Kp?

I think so, but if the question focus on pressures only or on concentrations only, just write Q or K should be fine. Just make sure you use the correct formula, do not write pressures of reactants/products for Kc/Qc and do not write concentration of reactants/products for Kp/Qp.

Rami_Z_AbuQubo_2K
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Re: Q and K

Postby Rami_Z_AbuQubo_2K » Sat Jan 12, 2019 10:41 am

K is the actual equilibrium constant that is a specific given value for a certain reaction. However, when you are calculating whether a reaction has reached equilibrium, you use Q, and compare it to the equilibrium constant K. If Q is equal to K, then the reaction is at equilibrium. Since K is a fixed value, if the calculated value of Q is smaller than K, the reaction will favor more products. However, if the calculated value of Q is greater than K, then the reaction will favor more reactants. K does not change but Q can depending on the conditions of the problem.

KatelinTanjuaquio 1L
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Re: Q and K

Postby KatelinTanjuaquio 1L » Sat Jan 12, 2019 1:22 pm

Q is calculated at any time during the reaction while K is only calculated at equilibrium. This means that Q and K would be equal if the point at which Q was measured was at equilibrium. Q is not limited to the concentration or partial pressures values at equilibrium, while K is.


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