Number of statement(s) that is/are correct :

(a) On increasing temperature, pH of pure water decreases

(b) On increasing temperature, pOH of pure water decreases 

(c) On increasing dilution, dissociation of weak electrolyte increases 

(d) pH of ${10}^{-7} \mathrm{M} \mathrm{NaOH}\left(\mathrm{aq}\right)$ is 7 at 25° C. 

(e) At equivalence point (during titration of acid and base) solution must be neutral. 

(f) Generally, pH of buffer solution does not change on dilution. 

(g) pH of salt of weak acid and weak base depends on concentration of salt.