I understand solids are insoluble and will just sit at the bottom of the vessel so we don't include them.

But I am confused as to why aqueous solutions are used in the equilibrium equation but liquids are not.

E.g. for the reaction:


The equilibrium constant is: enter image description here

Why isn't H20 (liquid) included in the equilibrium constant yet KCl (aq) is?

Thank you

  • $\begingroup$ An example would help. $\endgroup$ – Agriculturist Jul 7 '16 at 22:24
  • $\begingroup$ In the example you give, water would be excluded because it is the solvent of HCl and KOH (both are aqueous). Any change in water then, from the equilibrium, would be insignificant. $\endgroup$ – IT Tsoi Jul 8 '16 at 3:58

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