Calculating Kc

[Suraj Doshi 2G]

Why do we not include solids or liquids in the equilibrium concentration calculations?

[Kishan Shah 2G]

Basically solids and liquids have a constant concentration. There may be very tiny changes in volume of them but its not enough to affect our calculations. The activity of solids and liquids at equilibrium is 1, so therefore it doesn't affect equilibrium concentrations.

[stephaniekim2K]

Solids and liquids have constant concentrations so they don't change, so there is no need to calculate them.

[sarahforman_Dis2I]

Why do we not include solids or liquids in the equilibrium concentration calculations?

It is important to note that solvents (eg. liquid water) are not included in the equilibrium expression because only a minimal amount of the solvent is taken away in the reaction. Because of this, we can assume that the solvent concentration is essentially constant and therefore not include it in the equilibrium constant.

[Tiffany_Chen 2K]

Solids and liquids will hold relatively constant volume, thus you can technically "cancel" them out when putting products over reactants to find Kc.