Including H2O

[allyssa bradley 1H]

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]

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]

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]

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]

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

[Karl Yost 1L]

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]

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

[Lilly Catarozoli 1B]

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