---
title: "A student standardizes \\(\\text{NaOH(aq)}\\) by titrating a solution containing \\(1.20 \\times 10^{-3}\\ \\text{mol}\\) of dried potassium hydrogen phthalate, a monoprotic acid. The acid and \\(\\text{NaOH(aq)}\\) react in a \\(1:1\\) mole ratio. The buret was rinsed with the titrant before use. However, when the initial reading was taken, an air bubble occupying \\(0.40\\ \\text{mL}\\) remained in the buret tip below the stopcock. During the titration, the bubble was completely expelled and the tip filled with titrant before the endpoint was reached.  | Reading | Buret volume | |—|—| | Initial | \\(0.20\\ \\text{mL}\\) | | Final | \\(10.20\\ \\text{mL}\\) |  Assume that the endpoint was detected correctly and that there were no other experimental errors. Which statement correctly compares the calculated \\(\\text{NaOH(aq)}\\) concentration with its actual concentration?"
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url: "https://nerd-notes.com/ubq/120058/"
date_modified: "2026-08-21T08:41:03+00:00"
---

# A student standardizes \(\text{NaOH(aq)}\) by titrating a solution containing \(1.20 \times 10^{-3}\ \text{mol}\) of dried potassium hydrogen phthalate, a monoprotic acid. The acid and \(\text{NaOH(aq)}\) react in a \(1:1\) mole ratio. The buret was rinsed with the titrant before use. However, when the initial reading was taken, an air bubble occupying \(0.40\ \text{mL}\) remained in the buret tip below the stopcock. During the titration, the bubble was completely expelled and the tip filled with titrant before the endpoint was reached.

| Reading | Buret volume |
|—|—|
| Initial | \(0.20\ \text{mL}\) |
| Final | \(10.20\ \text{mL}\) |

Assume that the endpoint was detected correctly and that there were no other experimental errors. Which statement correctly compares the calculated \(\text{NaOH(aq)}\) concentration with its actual concentration?

A student standardizes \(\text{NaOH(aq)}\) by titrating a solution containing \(1.20 \times 10^{-3}\ \text{mol}\) of dried potassium hydrogen phthalate, a monoprotic acid. The acid and \(\text{NaOH(aq)}\) react in a \(1:1\) mole ratio. The buret was rinsed with the titrant before use. However, when the initial reading was taken, an air bubble occupying \(0.40\ \text{mL}\) remained in the buret tip below the stopcock. During the titration, the bubble was completely expelled and the tip filled with titrant before the endpoint was reached.

| Reading | Buret volume |
|---|---|
| Initial | \(0.20\ \text{mL}\) |
| Final | \(10.20\ \text{mL}\) |

Assume that the endpoint was detected correctly and that there were no other experimental errors. Which statement correctly compares the calculated \(\text{NaOH(aq)}\) concentration with its actual concentration?

- **A.** The calculated concentration, \(0.120\ \text{M}\), is too low because the trapped air dilutes the \(\text{NaOH(aq)}\) remaining in the buret.
- **B.** The calculated concentration, \(0.120\ \text{M}\), is too low because the recorded volume of \(10.00\ \text{mL}\) includes \(0.40\ \text{mL}\) used to fill the tip, so only \(9.60\ \text{mL}\) enters the flask.
- **C.** The calculated concentration, \(0.120\ \text{M}\), is too high because the actual volume entering the flask is only \(9.60\ \text{mL}\), which is less than the recorded volume.
- **D.** The calculated concentration, \(0.120\ \text{M}\), is equal to the actual concentration because reaching the endpoint fixes the moles of \(\text{NaOH(aq)}\) delivered regardless of the air bubble.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/120058/*