Calculating K

[Drew Myers 4G]

Why do we not include solids or liquids when calculating K?

[Sofia Ban]

we don't include those two states because molar concentration of a pure substance doesn't change in a reaction

[Jonathan Gong 2H]

Solids and liquids are excluded from the equilibrium expression because their concentrations stay constant throughout the reaction. In other words, they have no impact on reactant concentrations at equilibrium. Hope this helps.

[Cindy Adiwidjaja 1B]

We do not include solids and liquids when we calculate K because they stay constant and will ultimately have no effect on K. If you did want to include it, then you would still be essentially adding it to the top (products) and bottom (reactants) and they would still divide out to be 1.

[MaggieHan1L]

If you included it since the concentration doesn't change, the liquid and solid would just cancel out.

[Eva Zhao 4I]

Liquids and solids have an essentially constant concentration because they are practically incompressible. As a result, it takes enormous pressure to cause even a tiny reduction in volume. As such liquids and solids can be excluded from the equilibrium constant.