Question

question 29 (1 point)
use the following information to answer the next question.
hydrogen phosphate ion is an anion with the chemical
formula h₂po₄⁻. in the aqueous state, it undergoes the
following reactions:
(i) h₂po₄⁻(aq) + h₂o(l) → h₃o⁺(aq) + hpo₄²⁻(aq)
(ii) h₂po₄⁻(aq) + h₃o⁺(aq) → h₃po₄(aq) + h₂o(l)
which of the following statements is true about the above reactions?
○ in reaction (i) hydrogen phosphate acts as a brønsted acid and in reaction (ii) it
acts as a brønsted base.
○ in reaction (i) and (ii) hydrogen phosphate acts as a brønsted acid.
○ in reaction (i) and (ii) hydrogen phosphate acts as a brønsted base.
○ in reaction (i) hydrogen phosphate acts as a brønsted base and in reaction (ii) it
acts as a brønsted acid.
○ none of the above statements are true.

Explanation:

To solve this, we use the Brønsted - Lowry definitions: an acid donates a proton ($\ce{H+}$), and a base accepts a proton.

For reaction (i): $\ce{H2PO4^{-}(aq) + H2O(l) -> H3O^{+}(aq) + HPO4^{2 - }(aq)}$

In this reaction, $\ce{H2PO4^{-}}$ donates a proton ($\ce{H+}$) to $\ce{H2O}$. When a species donates a proton, it acts as a Brønsted acid. So, $\ce{H2PO4^{-}}$ is acting as a Brønsted acid here.

For reaction (ii): $\ce{H2PO4^{-}(aq) + H3O^{+}(aq) -> H3PO4(aq) + H2O(l)}$

Here, $\ce{H2PO4^{-}}$ accepts a proton ($\ce{H+}$) from $\ce{H3O^{+}}$. When a species accepts a proton, it acts as a Brønsted base. So, $\ce{H2PO4^{-}}$ is acting as a Brønsted base here.

So, in reaction (i) hydrogen phosphate acts as a Brønsted acid and in reaction (ii) it acts as a Brønsted base.

Answer:

A. In reaction (i) hydrogen phosphate acts as a Brønsted acid and in reaction (ii) it acts as a Brønsted base.