Solids and Liquids

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Diane Kang 2F
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Solids and Liquids

Postby Diane Kang 2F » Mon Jan 07, 2019 4:16 pm

Dr. Lavelle mentioned that solids and liquids are not included in K expressions because they are usually in excess.

But what if a solid or liquid in a chemical equation is a limiting reactant, thus not present in excess? Should their concentrations be included in K expressions?

Chem_Mod
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Re: Solids and Liquids

Postby Chem_Mod » Mon Jan 07, 2019 4:25 pm

We never include solids or liquids in equilibrium expressions.

Fayez Kanj
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Re: Solids and Liquids

Postby Fayez Kanj » Mon Jan 07, 2019 4:26 pm

Hello!

Dr Lavelle said in class that solids and liquids are not included in the equilibrium constants, not because they are in excess, rather because the molar concentrations of pure substances (ie: solids and liquids) does not change in a reaction. As such, in all cases, whether limiting or not, they are not included in the expressions.

Hope this helps :)

kamalkolluri
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Re: Solids and Liquids

Postby kamalkolluri » Mon Jan 07, 2019 4:43 pm

Another thing Lavelle said is there's no such thing as a concentration/partial pressure for solids and liquids, so they won't be included in your Kc or Kp.

Adam Vuilleumier 2K
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Re: Solids and Liquids

Postby Adam Vuilleumier 2K » Mon Jan 07, 2019 6:05 pm

To clear up what was said above, there is no way to determine the concentration of a solid, however, liquids are not included in the Kc for a different reason. Dr. Lavelle said that the amount of liquids, or solvents, on both sides of the reaction are almost the same. Thus, the concentrations cancel in the ratio of [P]/[R].


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