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### Calculating K

Posted: Sun Nov 13, 2016 2:55 pm
When calculating the equilibrium constant, what do you do if one of the reactants or products are a liquid or solid?

### Re: Calculating K

Posted: Sun Nov 13, 2016 3:26 pm
Liquids and solids are not included when trying to find the equilibrium constant. The molar concentration of a pure solid or liquid will not change in a reaction and therefore are disregarded.

### Re: Calculating K

Posted: Sun Nov 13, 2016 4:52 pm
One of our questions on the quiz seems to want us to do this. Question 8 on Fall 2014 prep says:

Considering NH4HS(s) <--> NH3(g) + H2S(g)

If Kp is 0.11 at 300K, calculate the equilibrium partial pressure of NH3(g) starting from pure NH4HS(s).

### Re: Calculating K

Posted: Mon Nov 14, 2016 4:32 pm
Even if there's a solid in the reaction, you can still calculate the Q and K using just the concentrations of the reactants and or products in gas phase.

### Re: Calculating K

Posted: Mon Nov 14, 2016 6:18 pm
When calculating equilibrium constants, we treat the concentrations of pure liquids and solids as if they were always exactly 1.