Consider the following polyprotic reactions:
H₃A (aq) + H₂O (l) ⇌ H₃O⁺ (aq) + H₂A (aq)
H₂A⁻ (aq) + H₂O (l) ⇌ H₃O⁺ (aq) + HA²⁻ (aq)
HA²⁻ (aq) + H₂O (l) ⇌ H₃O⁺ (aq) + A³⁻ (aq)
Ka1= 1.4 x 10⁻³
Ka₂= 1.1 x 10⁻⁷
Ka₃ 1.8 x 10⁻¹¹
If the targeted pH for your buffer is 7.5 what are the predominant proton donor and proton acceptor in solution? Below the answer options are in the order of proton donor/proton acceptor.
A) H₃A/H₂A⁻
B) H₂A⁻/HA2-
C) HA²⁻/H₂A⁻
D) H₃A/ A³⁻
E) H₂A⁻/H₃A