Reason (R) : The `pH` of an aqueous solution of `CH_(3)COOH` remains unchanged on the addition of `CH_(3)COONa`. Reason (R) : The ionisation of `CH_(3)COOH` is supressed by the addition of `CH_(3)COONa`. pH of an aqueous 0.1(M) `CH_(3)COOH` solution is 2.87.