A strong acid or base will completely disassociate, meaning that the acid will form two ions, #H^+# and its conjugate base. Strong acids completely disassociate because their conjugate base is weaker than water. This means that there is no equilibrium in the solution, simply because the bases aren't "strong" enough to bond to an #H^+# ion. Same applies for strong bases, but a strong base contains an #OH^-# ion.
#HCl + H_2O -> H_3O^++ Cl^-#
#HBr + H_2O -> H_3O^+ + Br^-#
#NaOH -> Na^+ + OH^-#
#Mg(OH)_2 -> Mg^-2 +2OH^-#
Weak acids and bases, however, do have the ability to bond to #H^+# ions after disassociation, therefore there is an equilibrium present in the solution.
