Q vs. K


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Hailey Johnson
Posts: 31
Joined: Wed Nov 16, 2016 3:04 am

Q vs. K

Postby Hailey Johnson » Sat Mar 03, 2018 9:58 pm

What is the difference between Q and K and how do we know which one to use in a given problem?

Lourick Bustamante 1B
Posts: 50
Joined: Wed Nov 16, 2016 3:02 am

Re: Q vs. K

Postby Lourick Bustamante 1B » Sat Mar 03, 2018 10:07 pm

Q is the the reaction quotient and K is the equilibrium constant. Both Q and K are calculated the same way (by using pressures or concentrations) but they are applied differently depending on the equation that you are using. Because they are calculated the same, it shouldn't make too much of a difference if you are calculating one or the other but the problem and equation should specify that for you.

Jessica_Singh_1J
Posts: 50
Joined: Fri Sep 29, 2017 7:03 am

Re: Q vs. K

Postby Jessica_Singh_1J » Sat Mar 03, 2018 10:24 pm

Q is the quotient calculated at non equilibrium conditions while K is the quotient calculated at equilibrium.

Sirajbir Sodhi 2K
Posts: 47
Joined: Sat Jul 22, 2017 3:00 am

Re: Q vs. K

Postby Sirajbir Sodhi 2K » Sat Mar 03, 2018 11:37 pm

In much of what we do, Q is used when we want to calculate some sort of potential at non-standard conditions (Gibbs Free Energy, Nernst Equation). K is used in our calculations when we want to calculate the potential at standard conditions, usually.

diangelosoriano
Posts: 49
Joined: Fri Sep 29, 2017 7:07 am

Re: Q vs. K

Postby diangelosoriano » Tue Mar 06, 2018 5:27 pm

You must also be sure to make the distinction between capital K and lowercase k when we deal with kinetics (rate constant).

Alex Nechaev 1I
Posts: 50
Joined: Fri Sep 29, 2017 7:04 am

Re: Q vs. K

Postby Alex Nechaev 1I » Mon Mar 12, 2018 8:16 pm

K can be used calculate the final concentrations at equilibrium for a reaction using an ICE table and the natural progression of the reaction, from left to right or from right to left. Q expresses the relative ratio of products to reactants at a given instant.

Rachel Wang
Posts: 49
Joined: Fri Sep 29, 2017 7:04 am

Re: Q vs. K

Postby Rachel Wang » Fri Mar 16, 2018 6:54 pm

K is the equilibrium constant. Q is the constant when the rxn isn't at equilibrium and when compared to K can predict which way the rxn will proceed at that particular state. They are calculated the same way.

704887365
Posts: 49
Joined: Sat Jul 22, 2017 3:00 am

Re: Q vs. K

Postby 704887365 » Fri Mar 16, 2018 7:18 pm

Q is calculated under conditions at any given time while K is calculated while the reaction is at equilibrium.

Michael Downs 1L
Posts: 29
Joined: Thu Jul 13, 2017 3:00 am

Re: Q vs. K

Postby Michael Downs 1L » Fri Mar 16, 2018 10:05 pm

Q is used to compare to K for some reactions


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