As we saw in the last lecture, calculations involving strong acids and bases are very straightforward. These species dissociate completely in water.  So, [strong acid] = [H+].  For strong bases, pay attention to theformula.  Groups I and II both form hydroxide (OH-) and oxide (O2-) salts.  NaOH will provide one mole of OH- per mole of salt, but Ca(OH)2 will provide two moles of OH- per mole of salt.  Once you know the [H+] or [OH-], it is easy to change these into pH or pOH quantities.