Explain why pure liquids and solids can ignored while writing the equilibrium constant expression?

Explanation

[Pure liquid ] or [Pure solid] =` (" No. of moles ")/(Volume in L) = ("Mass//mol.mass")/(Volume) = ("Mass")/("Volume") xx 1/("Mol .mass") = ("Density")/(" Mol . Mass") `
As demsity of a pure liquid or pure solid is constant at constant temperature and molecular mass is also constant , therefore , their molar concentrations are constant and included into the equilibrium constant .