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title: "A student standardizes an aqueous solution of sodium hydroxide, \\(\\text{NaOH(aq)}\\), by titrating it against potassium hydrogen phthalate, \\(\\text{KHC}_8\\text{H}_4\\text{O}_4\\) (molar mass \\(204.2 \\text{ g/mol}\\), abbreviated as \\(\\text{KHP}\\)). The student massed a sample of pure solid \\(\\text{KHP}\\) on an analytical balance, transferred it completely to an Erlenmeyer flask, and dissolved it in approximately \\(50 \\text{ mL}\\) of distilled water. Before titrating with \\(\\text{NaOH(aq)}\\) from a buret, the student rinsed the inner walls of the Erlenmeyer flask with an additional \\(15 \\text{ mL}\\) of distilled water to ensure all solid was in the solution. Which of the following best explains the effect of adding this additional distilled water on the calculated molarity of the \\(\\text{NaOH(aq)}\\) solution?"
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url: "https://nerd-notes.com/ubq/123633/"
date_modified: "2026-09-28T12:01:51+00:00"
---

# A student standardizes an aqueous solution of sodium hydroxide, \(\text{NaOH(aq)}\), by titrating it against potassium hydrogen phthalate, \(\text{KHC}_8\text{H}_4\text{O}_4\) (molar mass \(204.2 \text{ g/mol}\), abbreviated as \(\text{KHP}\)). The student massed a sample of pure solid \(\text{KHP}\) on an analytical balance, transferred it completely to an Erlenmeyer flask, and dissolved it in approximately \(50 \text{ mL}\) of distilled water. Before titrating with \(\text{NaOH(aq)}\) from a buret, the student rinsed the inner walls of the Erlenmeyer flask with an additional \(15 \text{ mL}\) of distilled water to ensure all solid was in the solution. Which of the following best explains the effect of adding this additional distilled water on the calculated molarity of the \(\text{NaOH(aq)}\) solution?

A student standardizes an aqueous solution of sodium hydroxide, \(\text{NaOH(aq)}\), by titrating it against potassium hydrogen phthalate, \(\text{KHC}_8\text{H}_4\text{O}_4\) (molar mass \(204.2 \text{ g/mol}\), abbreviated as \(\text{KHP}\)). The student massed a sample of pure solid \(\text{KHP}\) on an analytical balance, transferred it completely to an Erlenmeyer flask, and dissolved it in approximately \(50 \text{ mL}\) of distilled water. Before titrating with \(\text{NaOH(aq)}\) from a buret, the student rinsed the inner walls of the Erlenmeyer flask with an additional \(15 \text{ mL}\) of distilled water to ensure all solid was in the solution. Which of the following best explains the effect of adding this additional distilled water on the calculated molarity of the \(\text{NaOH(aq)}\) solution?

- **A.** The calculated molarity is too low because the added water decreases the concentration of \(\text{KHP}\), requiring a smaller volume of \(\text{NaOH(aq)}\) titrant to reach the equivalence point.
- **B.** The calculated molarity is unaffected because the added water does not change the total number of moles of \(\text{KHP}\) available to react with the \(\text{NaOH(aq)}\).
- **C.** The calculated molarity is unaffected because the added water dilutes both the \(\text{KHP}\) in the flask and the \(\text{NaOH(aq)}\) delivered from the buret by the same factor.
- **D.** The calculated molarity is too high because the added water increases the total volume of solution in the flask, requiring a larger volume of \(\text{NaOH(aq)}\) titrant to reach the equivalence point.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123633/*