Even though they have the same concentration they have different pH.
The pH of a strong base is determined by the pOH= -log10(OH-) Where the brackets correspond to molarity. Eg. Calculate the pH of 0.15 NaOH (Sodium hydroxide) solution.
pOH= -log10(0.15)
pOH= 0.82
Now you need to find pH of the base knowning that pOH + pH = 14
therefore ->
0.82 +pH = 14
pH = 13.18 of NaOH
In weak bases we find the (OH-) value by square rooting Kb multiplied by Mb where Mb is the molarity of the base and Kb is a value given for the dissociation constant of a weak base.
Eg. Ammonia is a weak base (as it does not accept protons (H+) easily) calculate the pH of ammonia if the molarity of NH3 is 0.15 moles/litre and the Kb is 1.8×10^-5.
(OH-) pH= √Kb × Mb
(OH-) = √1.8×10∧-5 ×0.15
(OH-) = .00164
pOH = -log10(OH-)
pOH= -log10(0.00164)
pOH = 2.785
pOH+pH = 14
2.785 + pH = 14
pH = 14 - 2.785
pH= 11.215 of NH3
Therefore these bases differ due to different pH also weak bases are poor proton acceptors and strong bases are good proton acceptors.
Hope this helps :).
