Understanding Q

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briannam_1F
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Understanding Q

When calculating for Q do we omit solids and pure liquids as well?

JohnWalkiewicz2J
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Re: Understanding Q

Considering you omit solids and liquids when calculating the equilibrium constant, I would say yes, leave out solids and liquids when calculating the reaction quotient.

sarahsalama2E
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Re: Understanding Q

Yes you would also leave out solids and liquids because their concentrations do not change. Also just to refresh, Q is the reaction quotient when the reaction is NOT at equilibrium and if Q <K, reaction favors the forward direction, and if Q>K, then reaction favors the backwards direction, and if Q=K, then the reaction is at equilibrium.

Vincent Leong 2B
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Re: Understanding Q

In the reaction, whether it's at equilibrium or not, solids and liquids are pure substances. This means, that no matter how the reaction goes, the overall reaction will not change the substance significantly enough for its concentration to change. That is why at equilibrium (for K constant) and the reaction quotient (Q), the concentration of that pure substance has no impact on the constant values -- because these substances have such an insignificant change in concentration that they practically cancel out when put into that ratio.

Pablo 1K
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Re: Understanding Q

Yes you would leave them out of your final expression.

Callum Guo 1H
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Re: Understanding Q

Yeah you only count things that are in aqeuous states and gas states if you are calculated the equilibrium for pressure

Jesse Anderson-Ramirez 3I
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Re: Understanding Q

When solving for Q you would leave out solids and liquids.

Juana Abana 1G
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Re: Understanding Q

Yes you would leave out solids and liquids.

Posts: 35
Joined: Tue Nov 05, 2019 12:18 am

Re: Understanding Q

Yes, you don't include solids and liquids, only whatever is in gaseous/aqueous states when calculating Q.

Megan Kirschner
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Re: Understanding Q

I understand the fact that you omit solids and liquids when calculating the equilibrium constant, but why? What's the logic behind it?

Leyna Dang 2H
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Re: Understanding Q

Megan Kirschner wrote:I understand the fact that you omit solids and liquids when calculating the equilibrium constant, but why? What's the logic behind it?

Solids and liquids aren't included because they do not have a significant effect on the concentration. Lavelle also mentioned during lecture that solids do not have concentrations, so it wouldn't make sense to include them.

205150314
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Joined: Wed Feb 20, 2019 12:16 am

Re: Understanding Q

briannam_1F wrote:When calculating for Q do we omit solids and pure liquids as well?

Yes you would leave them out because Q is pretty much K, with the difference being that Q is at any time during the reaction but you would calculate it the same way as K

RobertXu_2J
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Re: Understanding Q

Yes you would, because the calculations for Q are the same as for K, except that the values used may be different.

gabbymaraziti
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Joined: Wed Sep 18, 2019 12:19 am

Re: Understanding Q

I believe we would omit pure solids and liquids because Q is calculated in the same way as K.