Solid and Liquid

[Junwei Sun 4I]

Why is it that when we write the expression for K we don't include solid and liquid? Is it because their concentration does not change or is it that the change is insignificant? Also for solid and liquid do we always write them as 1 in the equilibrium expression?

[Hannah Romeo 1J]

Solids and liquids are not included in the K expression as they do not change their concentrations in a reaction as they are pure substances. Essentially, their value is 1 resulting in the K expression only including aqueous solutions.

[Alex Tchekanov Dis 2k]

You are correct that that the concentration change is insignificant. You definitely need some of the solid and liquid to make the product, but the concentration difference is negligible.

[Kishan Shah 2G]

Yes, the concentration change of solids and liquids is insignificant. If you think about it, if they do not affect the concentrations of reactants/products, then they serve no purpose in the equilibrium constant.

[Mariah]

Solids and liquids are not included in the K expression as they do not change their concentrations in a reaction as they are pure substances. Essentially, their value is 1 resulting in the K expression only including aqueous solutions.

As well as gases!!

[VLi_2B]

Solids and liquids are not included in the K expression as they do not change their concentrations in a reaction as they are pure substances. Essentially, their value is 1 resulting in the K expression only including aqueous solutions.

As well as gases!!

Wait, I thought gases were included in the K expression... Can someone reexplain this to me?