We have acidic buffer of ${\mathrm{CH}}_3\mathrm{COONa}$ and ${\mathrm{CH}}_3\mathrm{COOH}.$ One (or) more of the following operations will not change P^H
I) Diluting the mixture ten times
II) Adding excess HCl
III) Adding excess NaOH
IV Adding equal moles of ${\mathrm{CH}}_3\mathrm{COONa}$ and ${\mathrm{CH}}_3\mathrm{COOH}$ into the buffer
Select correct alternative