---
title: "Water autoionizes according to the following equation:  \\[ 2\\,\\text{H}_2\\text{O}(l) \\rightleftharpoons \\text{H}_3\\text{O}^+(\\text{aq}) + \\text{OH}^-(\\text{aq}) \\]  At an elevated temperature of \\(45\\ ^\\circ\\text{C}\\), the value of the autoionization constant, \\(K_w\\), is \\(4.0 \\times 10^{-14}\\). What is the hydronium ion concentration, \\([\\text{H}_3\\text{O}^+]\\), in a sample of pure water at this temperature?"
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url: "https://nerd-notes.com/ubq/119778/"
date_modified: "2026-08-21T08:12:19+00:00"
---

# Water autoionizes according to the following equation:

\[ 2\,\text{H}_2\text{O}(l) \rightleftharpoons \text{H}_3\text{O}^+(\text{aq}) + \text{OH}^-(\text{aq}) \]

At an elevated temperature of \(45\ ^\circ\text{C}\), the value of the autoionization constant, \(K_w\), is \(4.0 \times 10^{-14}\). What is the hydronium ion concentration, \([\text{H}_3\text{O}^+]\), in a sample of pure water at this temperature?

Water autoionizes according to the following equation:

\[ 2\,\text{H}_2\text{O}(l) \rightleftharpoons \text{H}_3\text{O}^+(\text{aq}) + \text{OH}^-(\text{aq}) \]

At an elevated temperature of \(45\ ^\circ\text{C}\), the value of the autoionization constant, \(K_w\), is \(4.0 \times 10^{-14}\). What is the hydronium ion concentration, \([\text{H}_3\text{O}^+]\), in a sample of pure water at this temperature?

- **A.** \(1.0 \times 10^{-7}\text{ M}\)
- **B.** \(2.0 \times 10^{-7}\text{ M}\)
- **C.** \(4.0 \times 10^{-7}\text{ M}\)
- **D.** \(2.0 \times 10^{-6}\text{ M}\)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119778/*