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title: "A student is instructed to prepare exactly \\(250.0 \\text{ mL}\\) of a \\(0.100 \\text{ M}\\) \\(\\text{CuSO}_4\\text{(aq)}\\) standard solution using solid copper(II) sulfate pentahydrate, \\(\\text{CuSO}_4 \\cdot 5\\text{H}_2\\text{O}\\) (molar mass \\(250. \\text{ g/mol}\\)). The student correctly calculates and measures \\(6.25 \\text{ g}\\) of the solid, dissolves it in approximately \\(100 \\text{ mL}\\) of distilled water in a beaker, quantitatively transfers the mixture into a \\(250.0 \\text{ mL}\\) volumetric flask, and adds distilled water. During the final dilution, the student accidentally adds water until the meniscus is approximately \\(5 \\text{ mm}\\) above the calibration mark on the neck of the flask. Which of the following correctly identifies the effect of this error on the actual concentration of the solution and the appropriate corrective action?"
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url: "https://nerd-notes.com/ubq/123635/"
date_modified: "2026-09-28T12:01:52+00:00"
---

# A student is instructed to prepare exactly \(250.0 \text{ mL}\) of a \(0.100 \text{ M}\) \(\text{CuSO}_4\text{(aq)}\) standard solution using solid copper(II) sulfate pentahydrate, \(\text{CuSO}_4 \cdot 5\text{H}_2\text{O}\) (molar mass \(250. \text{ g/mol}\)). The student correctly calculates and measures \(6.25 \text{ g}\) of the solid, dissolves it in approximately \(100 \text{ mL}\) of distilled water in a beaker, quantitatively transfers the mixture into a \(250.0 \text{ mL}\) volumetric flask, and adds distilled water. During the final dilution, the student accidentally adds water until the meniscus is approximately \(5 \text{ mm}\) above the calibration mark on the neck of the flask. Which of the following correctly identifies the effect of this error on the actual concentration of the solution and the appropriate corrective action?

A student is instructed to prepare exactly \(250.0 \text{ mL}\) of a \(0.100 \text{ M}\) \(\text{CuSO}_4\text{(aq)}\) standard solution using solid copper(II) sulfate pentahydrate, \(\text{CuSO}_4 \cdot 5\text{H}_2\text{O}\) (molar mass \(250. \text{ g/mol}\)). The student correctly calculates and measures \(6.25 \text{ g}\) of the solid, dissolves it in approximately \(100 \text{ mL}\) of distilled water in a beaker, quantitatively transfers the mixture into a \(250.0 \text{ mL}\) volumetric flask, and adds distilled water. During the final dilution, the student accidentally adds water until the meniscus is approximately \(5 \text{ mm}\) above the calibration mark on the neck of the flask. Which of the following correctly identifies the effect of this error on the actual concentration of the solution and the appropriate corrective action?

- **A.** The actual concentration is greater than \(0.100 \text{ M}\), and the student should use a dropper to remove liquid until the bottom of the meniscus is at the calibration mark.
- **B.** The actual concentration is less than \(0.100 \text{ M}\), and the student must discard the solution and restart because removing liquid will also remove dissolved solute.
- **C.** The actual concentration is less than \(0.100 \text{ M}\), and the student should use a dropper to remove liquid until the bottom of the meniscus is at the calibration mark.
- **D.** The actual concentration is equal to \(0.100 \text{ M}\), and the student should proceed without modification because the total moles of solute added remain unchanged.

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