Q vs K

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Eileen Si 1G
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Joined: Fri Aug 30, 2019 12:17 am

Q vs K

Postby Eileen Si 1G » Tue Jan 07, 2020 4:46 pm

This may be an obvious question, but what is the difference between Q (reaction quotient) and K (equilibrium constant)?

Alicia Lin 2F
Posts: 83
Joined: Wed Sep 18, 2019 12:17 am

Re: Q vs K

Postby Alicia Lin 2F » Tue Jan 07, 2020 4:48 pm

Q is calculated the same as K. However, Q is not necessarily at equilibrium while K is.

Giselle Littleton 1F
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Joined: Wed Sep 18, 2019 12:20 am

Re: Q vs K

Postby Giselle Littleton 1F » Tue Jan 07, 2020 4:54 pm

The reaction quotient Q describes the ratio of products to reactants when the reaction in a non-equilibrium state. K describes the same thing only when the reaction is at equilibrium.

Vicki Liu 2L
Posts: 101
Joined: Sat Aug 24, 2019 12:15 am

Re: Q vs K

Postby Vicki Liu 2L » Tue Jan 07, 2020 5:49 pm

Another important thing to note is that by comparing the values of Q and K, you can predict how the reaction will proceed. If Q=K, the reaction has reached equilibrium. If Q<K, the reaction will form more products and if Q>K, more reactants.

AKatukota
Posts: 100
Joined: Thu Jul 25, 2019 12:18 am

Re: Q vs K

Postby AKatukota » Tue Jan 07, 2020 8:02 pm

Q refers to the direction that the reaction will proceed in. You use Q in comparison to K. For example, if Q<K, then the reaction favors reactant production. If Q>K then it favors products. If Q=K, then the reaction is at equilibrium.

BCaballero_4F
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Re: Q vs K

Postby BCaballero_4F » Tue Jan 07, 2020 9:00 pm

K is used for when it is at equilibrium

Rida Ismail 2E
Posts: 139
Joined: Sat Sep 07, 2019 12:16 am

Re: Q vs K

Postby Rida Ismail 2E » Tue Jan 07, 2020 9:38 pm

K is strictly for when the equation is at equilibrium. If it is not at equilibrium then the constant Q is used but they are calculated the same way. Maybe comparisons can then be made about K through the values of Q surrounding it.

Dina 2k
Posts: 57
Joined: Wed Sep 18, 2019 12:17 am

Re: Q vs K

Postby Dina 2k » Tue Jan 07, 2020 10:37 pm

I'm not sure if this has been asked, but how did you guys come to the conclusion for the answer to 5G.11a. I understand that to find Q, its the same process as finding K, but the solution manual for 11a doesn't show that.

sarahsalama2E
Posts: 164
Joined: Fri Aug 30, 2019 12:16 am

Re: Q vs K

Postby sarahsalama2E » Tue Jan 07, 2020 10:42 pm

Yes, as mentioned above Q is not the same as K. Q is the reaction quotient and K is when the chemical reaction is at equilibrium ONLY. If q is less than K, then the reaction will proceed to the right and if q is greater than K then the reaction will proceed to the left.

Minh Ngo 4G
Posts: 137
Joined: Thu Jul 25, 2019 12:17 am

Re: Q vs K

Postby Minh Ngo 4G » Tue Jan 07, 2020 11:56 pm

K is the value of molarity of P/R at equilibrium while Q is not at equilibrium (usually at initial condition). They are, however, calculated the same. Molarity or partial pressure ratio of P/R

Emily Vainberg 1D
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Joined: Sat Jul 20, 2019 12:15 am

Re: Q vs K

Postby Emily Vainberg 1D » Wed Jan 08, 2020 9:31 am

Q and K are both calculated the same: Concentration of products/ concentration of reactants

The only difference is that K is used when the reaction is at equilibrium, which is a specific point. Q can be used throughout the reaction before equilibrium is reached. Comparing the two lets you predict which way the reaction will continue.

Kavya Immadisetty 2B
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Re: Q vs K

Postby Kavya Immadisetty 2B » Wed Jan 08, 2020 11:18 am

Although Q and K are calculated the same way, the difference is the state of the reaction at the time when this is calculated: Q can be any specific point of time while K must be when the reaction is at equilibrium.

Nicholas_Gladkov_2J
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Joined: Sat Aug 17, 2019 12:17 am

Re: Q vs K

Postby Nicholas_Gladkov_2J » Sat Jan 11, 2020 9:55 pm

Eileen Si 3G wrote:This may be an obvious question, but what is the difference between Q (reaction quotient) and K (equilibrium constant)?


k is a constant that is temperature dependent (one per temperature) that is solved when the reaction reached equilibrium. Q is when the reaction has not reached equilibrium, but is solved exactly like k.

Anushka Chauhan2B
Posts: 51
Joined: Sat Aug 24, 2019 12:16 am

Re: Q vs K

Postby Anushka Chauhan2B » Sat Jan 11, 2020 11:30 pm

The value of K is determined when the reaction is at equilibrium, while the value of Q is when the reaction is not at equilibrium.


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