5.Are pure solids included in equilibrium expressions? Explain your answer.

Pure solids or liquids are excluded from the equilibrium expression because their effective concentrations stay constant throughout the reaction. The concentration of a pure liquid or solid equals its density divided by its molar mass.

Explanation:

Hope this helps!!!

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.