${{\mathrm{Fe}}^{+3}}_{\left(\mathrm{aq}\right)}+{{\mathrm{SCN}}^{-}}_{\left(\mathrm{aq}\right)}\rightleftharpoons {{\left[\mathrm{Fe}\right(\mathrm{SCN}\left)\right]}^{+2}}_{\left(\mathrm{aq}\right)}$ is an example of ....

Irreversible process that attains equilibrium state

Reversible process that never attains equilibrium state

Heterogeneous equilibrium

Homogeneous equilibrium