Answer:
-0.1051
Explanation:
First, we need to find the degree of dissociation (α) of each of the groups using the Handerson-Halsebach equation:
pH = pKa + log (α/1-α)
log (α/1-α) = pH - pKa
log (1-α/α) = pKa - pH
1-α/α =[tex]10^{pKa - pH}[/tex]
1-α = [tex]10^{pKa - pH}[/tex]*α
α = [tex]\frac{1}{10^{pKa-pH} +1}[/tex]
So, fo the α-carboxyl group:
α = [tex]\frac{1}{10^{-6.03} +1}[/tex]
α = 1.0000
And for the α-amino group
α = [tex]\frac{1}{10^{0.93} +1}[/tex]
α = 0.1051
In the ionization, the α-carboxyl group goes from neutral to a negative ion with charge -1, and the α-amino group goes from a positive ion with charge +1 to a neutral compound. So, the net charge is how many ions are presented multiplied by the charge.
For the first one, the value of α is the value of ions, but for the second, α represents the neutral, so the ions are 1-α:
-1*(1.000) + (+1)*(1-0.1051) = -0.1051
