## Solid/Liquid in Reactions

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Olivia Young 1A
Posts: 60
Joined: Fri Sep 28, 2018 12:24 am

### Solid/Liquid in Reactions

Why is it that solids and liquids are not included in the K expression? Is there a specific reason or is it a general rule?

Emily Ng_4C
Posts: 65
Joined: Fri Sep 28, 2018 12:17 am

### Re: Solid/Liquid in Reactions

Solids are not included because they don't have a concentration because solids are usually pure. Liquids are not included because they usually exist as a solvent and thus has such a large concentration that it barely changes throughout the reaction.

Sarah_Kang_2K
Posts: 72
Joined: Fri Sep 28, 2018 12:23 am

### Re: Solid/Liquid in Reactions

Solids aren't included in the equilibrium constant because there is no such thing as "concentration of a solid".
For liquids, liquids act as a solvent, and the change in concentration of a solvent is insignificant. Thus, we don't include pure liquids in the equilibrium constant.

904914909
Posts: 60
Joined: Fri Sep 28, 2018 12:26 am

### Re: Solid/Liquid in Reactions

Solids and liquid concentration can't change and so they don't have any effect on the equilibrium constant

Kate_Santoso_4F
Posts: 72
Joined: Fri Sep 28, 2018 12:29 am

### Re: Solid/Liquid in Reactions

Some reactions in solution involve the solvent as a reactant or product. When the solution is very dilute, the change in solvent concentration due to the reaction is insignificant so the solvent can be treated as a pure substance just like a solid. Also, the activity of a pure solid or liquid is 1 so even if you did plug it into the formula for the K expression, it would be insignificant mathematically.