Q.

The pKb of dimethylamine and pKa of acetic acid are 3.27 and 4.77 respectively at T(K). The correct option for the pH of dimethylammonium acetate solution is                [2021]

1 6.25  
2 8.50  
3 5.50  
4 7.75  

Ans.

(4)

For a salt of weak acid and weak base

            pH=7+12(pKa-pKb)

Given, pKa=4.77,pKb=3.27

           pH=7+12(4.77-3.27)=7.75