Since HCl is strong acid , it dissociates fully to give H+ and Cl - so the concentration of H+ = 2 M so p H = - log[H+] = - log (2) = - 0.301 Solution Since HCl is strong acid , it dissociates fully to give H+ and Cl - so the concentration of H+ = 2 M so p H = - log[H+] = - log (2) = - 0.301.