Answer:
C) H₂PO₄⁻(aq) + H₂O(l) → H₃O⁺(aq) + HPO₄²⁻(aq)
Explanation:
<em>For which of the following equilibria does Kc correspond to the acid-dissociation constant, Ka, of H₂PO₄⁻?
</em>
<em>A) H₂PO₄⁻(aq) + H₃O⁺(aq) → H₃PO₄(aq) + H₂O(l)
</em>
NO. This is the inverse of the acid dissociation of H₃PO₄.
<em>B) H₂PO₄⁻(aq) + H₂O(l) → H₃PO₄(aq) + OH⁻(aq)
</em>
NO. This is the basic dissociation of H₂PO₄⁻.
<em>C) H₂PO₄⁻(aq) + H₂O(l) → H₃O⁺(aq) + HPO₄²⁻(aq)
</em>
YES. This is the acid dissociation of H₂PO₄⁻. The acid-dissociation constant is:
<em>D) H₃PO₄(aq) + H₂O(l) → H₃O⁺(aq) + H₂PO₄⁻(aq)
</em>
No. This is the acid dissociation of H₃PO₄.
<em>E) HPO₄²⁻(aq) + H₂O(l) → H₂PO₄⁻(aq) + OH⁻(aq)</em>
NO. This is the basic dissociation of HPO₄²⁻.