Q & K?


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Guadalupe T 1E
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Joined: Fri Sep 29, 2017 7:04 am

Q & K?

Postby Guadalupe T 1E » Tue Feb 20, 2018 7:20 pm

I know when products/reactants are favored in terms of K>1 etc, but what are the rules when Q>K or Q<K?

Alyssa Parry Disc 1H
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Joined: Sat Jul 22, 2017 3:01 am

Re: Q & K?

Postby Alyssa Parry Disc 1H » Tue Feb 20, 2018 7:54 pm

I think that was just for Chem 14A

Daniisaacson2F
Posts: 30
Joined: Sat Jul 22, 2017 3:00 am

Re: Q & K?

Postby Daniisaacson2F » Wed Feb 21, 2018 2:26 pm

In the problems that they are giving in the homework, they are treating Q as if it was K, and using that value to determine whether the reactants or products are favored. In other words, they usually will not give you a K value to compare it to.

Sarkis Sislyan 1D
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Joined: Thu Jul 27, 2017 3:00 am

Re: Q & K?

Postby Sarkis Sislyan 1D » Wed Feb 21, 2018 3:41 pm

If Q>K then that means there is more product than at the equilibrium concentration. As such, LeChatelier's principle tells us that the reactants will be favored. If Q<K then that means there is more reactant than at the equilibrium concentration, so the products will be favored.

McKenna disc 1C
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Re: Q & K?

Postby McKenna disc 1C » Wed Feb 21, 2018 4:18 pm

Sarkis Sislyan 1D wrote:If Q>K then that means there is more product than at the equilibrium concentration. As such, LeChatelier's principle tells us that the reactants will be favored. If Q<K then that means there is more reactant than at the equilibrium concentration, so the products will be favored.


Yep! Q just has to do with the concentrations of the reaction's components at any time. The equation's format is the same for Q as it is for K-- concentration of products raised to the powers of their stoichiometric coefficients divided by concentrations of reactants raised to the powers of their stoichiometric coefficients. The only difference is that Q can be measured at any time, whereas K refers only to equilibrium concentrations. And just as the reply above this explains, the direction in which the reaction will proceed depends on Q with respect to K. :) Hope this helps!


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