I understand you compare Ka values to determine the pH but this order just seems to be all over the place? HCl: strong acid so low pH C6H5NH3Cl: Ka=1.35x10^-5 NH4+ Ka=5.56x10^-10 MgCl2=neutral HClO2Ka=1.2x10^-2 HOCl Ka=4.0x10^-8
Some of these are tricky because the problem gives you the acid
In the case of the two species that have sodium (above), you have to use the
HCl comes apart, so that will be lowest pH.
The next options on the list for lowest pH are
HOCl is a weaker acid, so it will have a stronger conjugate base.
This means NaOCl will make a more basic solution than will
I hope that helps.