Question

Phosphate is derived from the titration of phosphoric acid, H3PO4. The three pKa’s of H3PO4 are 2.15, 7.20, and 12.35 respectively. 
a/ Write out the series of ionization (equilibrium) reactions corresponding to each ionization, making sure to write out the (flat) structure each molecule/ion as you do so. Mark correct chemical bonds.

b/ In your diagram above, circle the dominant form of phosphate as it would appear at pH 5.7.

Answer 1

Answer:

Answers are in the explanation

Explanation:

The equilibriums corresponding for each ionization are:

H₃PO₄ ⇄ H₂PO₄⁻ + H⁺ pka: 2,15

H₂PO₄⁻ ⇄ HPO₄²⁻ + H⁺ pka: 7,20

HPO₄²⁻ ⇄ PO₄³⁻ + H⁺ pka: 12,35

At pH 5,7 all H₃PO₄ reacts to produce H₂PO₄⁻ and the consumed H₂PO₄⁻ to form HPO₄²⁻ is not relevant yet. Thus, dominant for is H₂PO₄⁻

I hope it helps!