The structure of aspartic acid is given below 

(A) .

 

The pKa₁, pKa₂, and pKa₃ of (A), respectively, are:1.88, 3.65 and 9.60. pKa₁ corresponds to the ionization of the COOH group, of

. pKa₂ corresponds to the ionisation of $\left(\begin{array}{c}+\\ {\mathrm{NH}}_3\end{array}\right)$(ammonium ion). What is the pH at isoelectric points (pI)?

The pK_a value indicates the strength of an acid. pK_a is the negative log of the acid dissociation constant or Ka value. A lower pK_a value indicates a stronger acid. If there are more than one carboxylic group then we will take the average of pK_a of carboxyl groups $\mathrm{pH}=\frac{{\mathrm{pK}}_{{\mathrm{a}}_1}+{\mathrm{pKa}}_2}{2}$Hence, the correct options is(1)