We know that,
pH = -log [H+] and pOH = -log [OH-]
When water is used as a solvent pH + pOH = 14
Given [OH-] = 2.73 X 10-5 mol/dm3
∴ pOH = -log (2.73 X 10-5)
= 5
Thus, pH = 14 - pOH - 14 - 5 = 9
Here, ∵ pH is > 7, it suggest that solution is basic in nature.