Aspartic acid C4H7NO4 one of the 20 essential amino acids ha

Aspartic acid (C4H7NO4), one of the 20 essential amino acids, has two ionizable hydrogens. At 25 degrees C, Ka1=1.38 x 10-4 and Ka2=1.51 x 10-10. What is the concentration of doubly ionized asparate ions in a 0.125 M aqueous solution of aspartic acid?

Solution

C4H7NO4 <-----> C4H6NO4- + H+
initial concentration
0.125
change
-x .. . .. . .. . . . . . . .+x. .. . . . . +x

Ka1 = 1.38 x 10^-4 = x^2 / 0.125-x

x = [H+]= 0.00415 M

pH = 2.4

we can neglet the [H+] from the 2nd dissociation