---
title: "A student analyzes a treated-water sample at \\(25^\\circ\\text{C}\\). The hydroxide ion concentration of the sample is \\(2.0 \\times 10^{-4}\\text{ M}\\). At this temperature, \\(K_w=[\\text{H}_3\\text{O}^+][\\text{OH}^-]=1.0 \\times 10^{-14}\\).  What is the hydronium ion concentration of the sample?"
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url: "https://nerd-notes.com/ubq/119352/"
date_modified: "2026-08-19T12:39:56+00:00"
---

# A student analyzes a treated-water sample at \(25^\circ\text{C}\). The hydroxide ion concentration of the sample is \(2.0 \times 10^{-4}\text{ M}\). At this temperature, \(K_w=[\text{H}_3\text{O}^+][\text{OH}^-]=1.0 \times 10^{-14}\).

What is the hydronium ion concentration of the sample?

A student analyzes a treated-water sample at \(25^\circ\text{C}\). The hydroxide ion concentration of the sample is \(2.0 \times 10^{-4}\text{ M}\). At this temperature, \(K_w=[\text{H}_3\text{O}^+][\text{OH}^-]=1.0 \times 10^{-14}\).

What is the hydronium ion concentration of the sample?

- **A.** \(2.0 \times 10^{-18}\text{ M}\)
- **B.** \(5.0 \times 10^{-15}\text{ M}\)
- **C.** \(2.5 \times 10^{-11}\text{ M}\)
- **D.** \(5.0 \times 10^{-11}\text{ M}\)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119352/*