Page 1 of 1

Solids and liquids

Posted: Tue Nov 28, 2017 4:02 pm
by Liam Maxwell 2E
Why exactly aren't solids and liquids included in the equation to determine K. I vaguely remember in lecture Professor Lavelle touched on the point that they don't change in concentration, but what does that have to do with them being omitted from the equation.

Re: Solids and liquids

Posted: Tue Nov 28, 2017 4:13 pm
by Andrea ORiordan 1L
Liquids and solids are omitted from the equilibrium constant expression because, as you said, they do not change in concentration. Solids and liquids are virtually incompressible compared to gases. Pressure changes won't really affect the volume of a liquid or solid sample, whereas pressure changes will greatly affect the volume of a gaseous sample (which will greatly change the concentration).

Remember that the equilibrium constant/reaction quotient compares concentrations. If concentrations of solids and liquids rarely change, we can safely omit them from the expression.