Including H2O

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allyssa bradley 1H
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Joined: Wed Sep 30, 2020 9:47 pm

Including H2O

Postby allyssa bradley 1H » Thu Jan 07, 2021 2:45 pm

A couple hypothetical situations -- If an aqueous reaction needs a certain amount of water to balance the reaction, do we include it in K?
And in any formula, is liquid water still included in K when it just appears on one side of a balanced homogenous reaction?

Courtney Situ 2B
Posts: 104
Joined: Wed Sep 30, 2020 10:03 pm

Re: Including H2O

Postby Courtney Situ 2B » Thu Jan 07, 2021 2:54 pm

Hello!

Since water in an aqueous reaction is technically a pure liquid (the solvent), we can ignore it in the K calculations. Alternatively, we could write it in the K calculations, but the concentration of water would be 1 because it is the solvent. Therefore, the K value would not change.

Hope that helps!

Marisa Gaitan 2D
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Re: Including H2O

Postby Marisa Gaitan 2D » Thu Jan 07, 2021 3:09 pm

To answer your second question, no liquids are included, so even if liquid H2O was included only on one side, it would not have to be taken into consideration when calculating K.

Samiha Molla 3G
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Re: Including H2O

Postby Samiha Molla 3G » Thu Jan 07, 2021 3:14 pm

I don't think we need to ever include liquids because the change in concentration is usually too small to have an effect on the K value.

Jordan Tatang 3L
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Re: Including H2O

Postby Jordan Tatang 3L » Thu Jan 07, 2021 4:32 pm

I believe the general rule is to not include solids and liquids in the calculation of K

Karl Yost 1L
Posts: 162
Joined: Thu Dec 17, 2020 12:19 am

Re: Including H2O

Postby Karl Yost 1L » Thu Jan 07, 2021 5:52 pm

Liquid water is never included, as its change in concentration is deemed negligible. Only include gaseous water in ICE tables and K expressions, as its concentration can change.

Katie Le 3K
Posts: 73
Joined: Wed Sep 30, 2020 9:35 pm

Re: Including H2O

Postby Katie Le 3K » Thu Jan 07, 2021 6:07 pm

H2O in liquid form is not included along w/ solids.

Lilly Catarozoli 1B
Posts: 109
Joined: Wed Sep 30, 2020 9:53 pm

Re: Including H2O

Postby Lilly Catarozoli 1B » Thu Jan 07, 2021 6:17 pm

Liquids and solids are never included in K calculations because they don't have a concentration.


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