---
title: "A student performs a gravimetric analysis to determine the mass percent of \\(\\text{Cl}^-\\) in a solid mixture containing \\(\\text{NaCl}\\) and unreactive water-soluble impurities. The student dissolves a sample of the mixture in distilled water, adds an excess of \\(0.20 \\text{ M } \\text{AgNO}_3\\text{(aq)}\\) to precipitate all chloride ions as \\(\\text{AgCl(s)}\\), collects the precipitate by vacuum filtration, and dries the precipitate to constant mass. The experimental data are recorded in the table below.  | Measurement | Mass | | :— | :— | | Mass of unknown mixture sample | \\(1.000 \\text{ g}\\) | | Mass of dry filter paper | \\(0.850 \\text{ g}\\) | | Mass of filter paper \\(+\\) dry \\(\\text{AgCl(s)}\\) | \\(2.284 \\text{ g}\\) |  Based on the data collected, what is the mass percent of \\(\\text{Cl}^-\\) in the original sample, and how would failing to rinse the precipitate with distilled water before drying affect the calculated mass percent of \\(\\text{Cl}^-\\)?"
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url: "https://nerd-notes.com/ubq/123657/"
date_modified: "2026-09-28T12:01:54+00:00"
---

# A student performs a gravimetric analysis to determine the mass percent of \(\text{Cl}^-\) in a solid mixture containing \(\text{NaCl}\) and unreactive water-soluble impurities. The student dissolves a sample of the mixture in distilled water, adds an excess of \(0.20 \text{ M } \text{AgNO}_3\text{(aq)}\) to precipitate all chloride ions as \(\text{AgCl(s)}\), collects the precipitate by vacuum filtration, and dries the precipitate to constant mass. The experimental data are recorded in the table below.

| Measurement | Mass |
| :— | :— |
| Mass of unknown mixture sample | \(1.000 \text{ g}\) |
| Mass of dry filter paper | \(0.850 \text{ g}\) |
| Mass of filter paper \(+\) dry \(\text{AgCl(s)}\) | \(2.284 \text{ g}\) |

Based on the data collected, what is the mass percent of \(\text{Cl}^-\) in the original sample, and how would failing to rinse the precipitate with distilled water before drying affect the calculated mass percent of \(\text{Cl}^-\)?

A student performs a gravimetric analysis to determine the mass percent of \(\text{Cl}^-\) in a solid mixture containing \(\text{NaCl}\) and unreactive water-soluble impurities. The student dissolves a sample of the mixture in distilled water, adds an excess of \(0.20 \text{ M } \text{AgNO}_3\text{(aq)}\) to precipitate all chloride ions as \(\text{AgCl(s)}\), collects the precipitate by vacuum filtration, and dries the precipitate to constant mass. The experimental data are recorded in the table below.

| Measurement | Mass |
| :--- | :--- |
| Mass of unknown mixture sample | \(1.000 \text{ g}\) |
| Mass of dry filter paper | \(0.850 \text{ g}\) |
| Mass of filter paper \(+\) dry \(\text{AgCl(s)}\) | \(2.284 \text{ g}\) |

Based on the data collected, what is the mass percent of \(\text{Cl}^-\) in the original sample, and how would failing to rinse the precipitate with distilled water before drying affect the calculated mass percent of \(\text{Cl}^-\)?

- **A.** \(35.5\%\); the calculated value would be too high because residual dissolved ions crystallize on the filter paper upon drying, increasing the measured precipitate mass.
- **B.** \(35.5\%\); the calculated value would be too low because unreacted \(\text{Ag}^+\text{(aq)}\) remaining on the filter paper prevents complete precipitation of \(\text{AgCl(s)}\).
- **C.** \(58.4\%\); the calculated value would be too high because residual dissolved ions crystallize on the filter paper upon drying, increasing the measured precipitate mass.
- **D.** \(58.4\%\); the calculated value would be too low because unreacted \(\text{Ag}^+\text{(aq)}\) remaining on the filter paper prevents complete precipitation of \(\text{AgCl(s)}\).

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123657/*