${\mathrm{K}}_{\mathrm{a}}$ for ${\mathrm{CH}}_{3}\mathrm{COOH}$ is $1.8×{10}^{-5}$ and Kb for ${\mathrm{NH}}_{4}\mathrm{OH}$ is $1.8×{10}^{-5}$. The pH of ammonium acetate will be

(1) 7.005

(2) 4.75

(3) 7.0

(4) Between 6 and 7

Hint: $\mathrm{pH}=7+\frac{{\mathrm{pK}}_{\mathrm{a}}-{\mathrm{pK}}_{\mathrm{b}}}{2}$
Given that,
Ammonium acetate is a salt of a weak acid and weak acid. For such salts