---
title: "A buffer solution at a physiological \\(\\text{pH}\\) of \\(7.40\\) is prepared by mixing appropriate amounts of sodium dihydrogen phosphate, \\(\\text{NaH}_2\\text{PO}_4\\), and sodium hydrogen phosphate, \\(\\text{Na}_2\\text{HPO}_4\\). The acid-base equilibrium is represented by the equation below:  \\[ \\text{H}_2\\text{PO}_4^-\\text{(aq)} + \\text{H}_2\\text{O(l)} \\rightleftharpoons \\text{HPO}_4^{2-}\\text{(aq)} + \\text{H}_3\\text{O}^+\\text{(aq)} \\quad \\text{p}K_a = 7.10 \\]  Given that \\(\\log(2.0) \\approx 0.30\\), what is the required molar concentration ratio of \\(\\dfrac{[\\text{HPO}_4^{2-}]}{[\\text{H}_2\\text{PO}_4^-]}\\) in this buffer?"
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url: "https://nerd-notes.com/ubq/119992/"
date_modified: "2026-08-21T08:31:40+00:00"
---

# A buffer solution at a physiological \(\text{pH}\) of \(7.40\) is prepared by mixing appropriate amounts of sodium dihydrogen phosphate, \(\text{NaH}_2\text{PO}_4\), and sodium hydrogen phosphate, \(\text{Na}_2\text{HPO}_4\). The acid-base equilibrium is represented by the equation below:

\[ \text{H}_2\text{PO}_4^-\text{(aq)} + \text{H}_2\text{O(l)} \rightleftharpoons \text{HPO}_4^{2-}\text{(aq)} + \text{H}_3\text{O}^+\text{(aq)} \quad \text{p}K_a = 7.10 \]

Given that \(\log(2.0) \approx 0.30\), what is the required molar concentration ratio of \(\dfrac{[\text{HPO}_4^{2-}]}{[\text{H}_2\text{PO}_4^-]}\) in this buffer?

A buffer solution at a physiological \(\text{pH}\) of \(7.40\) is prepared by mixing appropriate amounts of sodium dihydrogen phosphate, \(\text{NaH}_2\text{PO}_4\), and sodium hydrogen phosphate, \(\text{Na}_2\text{HPO}_4\). The acid-base equilibrium is represented by the equation below:

\[ \text{H}_2\text{PO}_4^-\text{(aq)} + \text{H}_2\text{O(l)} \rightleftharpoons \text{HPO}_4^{2-}\text{(aq)} + \text{H}_3\text{O}^+\text{(aq)} \quad \text{p}K_a = 7.10 \]

Given that \(\log(2.0) \approx 0.30\), what is the required molar concentration ratio of \(\dfrac{[\text{HPO}_4^{2-}]}{[\text{H}_2\text{PO}_4^-]}\) in this buffer?

- **A.** \(0.30\)
- **B.** \(0.50\)
- **C.** \(1.3\)
- **D.** \(2.0\)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119992/*