Liquids and Solids

[Kimberly 1H]

Why aren't reactants and products in the liquid and solid phases not included when calculating K?

[Jessica Tsui 1H]

I think Professor Lavelle said it's because solids and liquids aren't changed in concentration during the reaction.

[Kevin Tang 4L]

Solids have a concentration of 1, which doesn't change anything in the equilibrium concentration equation.
For example, C(s)+ O(g) <-> CO(g), if Carbon was included in K because it was, it would be [CO]/[O]*1 which is just [CO]/[O].
You don't want to include the concentration of Carbon though, as it may show a lack of understanding in concentrations.

Hope this helps and correct me if I'm wrong.

[305113590]

Solids and liquids (pure substances) are incompressible and concentration don't change (or change very insignificantly) throughout the reaction. For example, pure water in the liquid or solid phase is 100% water and incompressible. Hence, water doesn't influence the reaction.