For the reaction  Pt /H₂(1atm) / H⁺_(aq) // Cl^–_(aq) /AgCl/Ag  K_c (equilibrium constant) is represented as

From the given cell notation the cell reaction is

$\text{ Anode : }\frac{1}{2}{\mathrm{H}}_{2\left(1\mathrm{atm}\right)}\rightleftharpoons {\mathrm{H}}_{\left(\mathrm{aq}\right)}^{+}+{\mathrm{e}}^{-}$

$\text{ Cathode: }{\mathrm{AgCl}}_{\left(\mathrm{s}\right)}+{\mathrm{e}}^{-}\rightleftharpoons {\mathrm{Ag}}_{\left(\mathrm{s}\right)}+{\mathrm{Cl}}_{\left(\mathrm{aq}\right)}^{-}$

${\mathrm{AgCl}}_{\left(\mathrm{s}\right)}+\frac{1}{2}{\mathrm{H}}_{2\left(1\mathrm{atm}\right)}\rightleftharpoons {\mathrm{H}}_{\left(\mathrm{aq}\right)}^{+}+{\mathrm{Cl}}_{\left(\mathrm{aq}\right)}^{-}+{\mathrm{Ag}}_{\left(\mathrm{s}\right)}$

${\mathrm{K}}_{\mathrm{C}}=\left[{\mathrm{H}}^{+}\right]\left[{\mathrm{Cl}}^{-}\right]$

For  all Solids and pure liquids, active mass = 1