The equilibrium constant of a reaction only involving pure solid or liquid How to calculate the equilibrium constant of a reaction only involving pure solid or liquid.
For example reaction
$$\ce{S(s) + Hg(l) -&gt; HgS(s)}$$
or
$$\ce{S(s) + Mg(s) -&gt; MgS(s)}$$
Concentration of  pure solids and liquids is conventionally taken to be 1. Since reaction involves only solids and liquids the equilibrium constant will be 1