---
title: "A student combines a phosphate-buffered water sample with a bicarbonate-containing water sample in a sealed flask. The following proton-transfer equilibrium is considered.  \\[ \\text{H}_2\\text{PO}_4^-\\text{(aq)}+\\text{HCO}_3^-\\text{(aq)}\\rightleftharpoons \\text{HPO}_4^{2-}\\text{(aq)}+\\text{H}_2\\text{CO}_3\\text{(aq)} \\]  Independent measurements at the same temperature establish that \\(\\text{H}_2\\text{CO}_3\\) is a stronger Brønsted–Lowry acid than \\(\\text{H}_2\\text{PO}_4^-\\). Which choice correctly identifies the roles of the species in the reaction as written and the side favored at equilibrium?"
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url: "https://nerd-notes.com/ubq/120117/"
date_modified: "2026-08-21T08:41:52+00:00"
---

# A student combines a phosphate-buffered water sample with a bicarbonate-containing water sample in a sealed flask. The following proton-transfer equilibrium is considered.

\[
\text{H}_2\text{PO}_4^-\text{(aq)}+\text{HCO}_3^-\text{(aq)}\rightleftharpoons \text{HPO}_4^{2-}\text{(aq)}+\text{H}_2\text{CO}_3\text{(aq)}
\]

Independent measurements at the same temperature establish that \(\text{H}_2\text{CO}_3\) is a stronger Brønsted–Lowry acid than \(\text{H}_2\text{PO}_4^-\). Which choice correctly identifies the roles of the species in the reaction as written and the side favored at equilibrium?

A student combines a phosphate-buffered water sample with a bicarbonate-containing water sample in a sealed flask. The following proton-transfer equilibrium is considered.

\[
\text{H}_2\text{PO}_4^-\text{(aq)}+\text{HCO}_3^-\text{(aq)}\rightleftharpoons \text{HPO}_4^{2-}\text{(aq)}+\text{H}_2\text{CO}_3\text{(aq)}
\]

Independent measurements at the same temperature establish that \(\text{H}_2\text{CO}_3\) is a stronger Brønsted–Lowry acid than \(\text{H}_2\text{PO}_4^-\). Which choice correctly identifies the roles of the species in the reaction as written and the side favored at equilibrium?

- **A.** \(\text{H}_2\text{PO}_4^-\): base; \(\text{HPO}_4^{2-}\): conjugate acid; \(\text{HCO}_3^-\): acid; \(\text{H}_2\text{CO}_3\): conjugate base; reactants favored
- **B.** \(\text{H}_2\text{PO}_4^-\): acid; \(\text{HPO}_4^{2-}\): conjugate base; \(\text{HCO}_3^-\): acid; \(\text{H}_2\text{CO}_3\): conjugate base; reactants favored
- **C.** \(\text{H}_2\text{PO}_4^-\): acid; \(\text{HPO}_4^{2-}\): conjugate base; \(\text{HCO}_3^-\): base; \(\text{H}_2\text{CO}_3\): conjugate acid; products favored
- **D.** \(\text{H}_2\text{PO}_4^-\): acid; \(\text{HPO}_4^{2-}\): conjugate base; \(\text{HCO}_3^-\): base; \(\text{H}_2\text{CO}_3\): conjugate acid; reactants favored

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/120117/*