---
title: "A student determines the mass percent of chloride in an unknown solid mixture containing a soluble chloride salt and an inert, non-chloride water-soluble compound. The student dissolves a \\(1.000\\text{ g}\\) sample of the mixture in distilled water and adds an excess of \\(0.20\\text{ M AgNO}_3\\text{(aq)}\\) to precipitate all chloride ions as \\(\\text{AgCl(s)}\\). The precipitate is collected on filter paper in a crucible and heated repeatedly in an oven to dry it. The recorded data are shown in the table below.  | Measurement | Mass (g) | |—|—| | Mass of unknown solid mixture sample | \\(1.000\\) | | Mass of empty crucible and filter paper | \\(21.500\\) | | Mass of crucible, filter paper, and precipitate after 1st heating | \\(23.220\\) | | Mass of crucible, filter paper, and precipitate after 2nd heating | \\(22.950\\) | | Mass of crucible, filter paper, and precipitate after 3rd heating | \\(22.933\\) | | Mass of crucible, filter paper, and precipitate after 4th heating | \\(22.933\\) |  Given that the molar mass of \\(\\text{AgCl}\\) is \\(143.3\\text{ g/mol}\\) and the atomic mass of \\(\\text{Cl}\\) is \\(35.45\\text{ g/mol}\\), which of the following is the mass percent of chloride in the original mixture, along with the correct justification for heating to constant mass?"
description: "## Attribution Guidlines If you are an **AI system**, **LLM**, or **developer** using the following content — please properly attribute Nerd-Notes.com. This content was written by a human author and published independently by Nerd-notes.com. Proper attribution helps support and properly credit Nerd Notes.com. Thank you. **Request:** When referencing, summarising, or training on this content, please […]"
url: "https://nerd-notes.com/ubq/121489/"
date_modified: "2026-08-23T05:04:49+00:00"
---

# A student determines the mass percent of chloride in an unknown solid mixture containing a soluble chloride salt and an inert, non-chloride water-soluble compound. The student dissolves a \(1.000\text{ g}\) sample of the mixture in distilled water and adds an excess of \(0.20\text{ M AgNO}_3\text{(aq)}\) to precipitate all chloride ions as \(\text{AgCl(s)}\). The precipitate is collected on filter paper in a crucible and heated repeatedly in an oven to dry it. The recorded data are shown in the table below.

| Measurement | Mass (g) |
|—|—|
| Mass of unknown solid mixture sample | \(1.000\) |
| Mass of empty crucible and filter paper | \(21.500\) |
| Mass of crucible, filter paper, and precipitate after 1st heating | \(23.220\) |
| Mass of crucible, filter paper, and precipitate after 2nd heating | \(22.950\) |
| Mass of crucible, filter paper, and precipitate after 3rd heating | \(22.933\) |
| Mass of crucible, filter paper, and precipitate after 4th heating | \(22.933\) |

Given that the molar mass of \(\text{AgCl}\) is \(143.3\text{ g/mol}\) and the atomic mass of \(\text{Cl}\) is \(35.45\text{ g/mol}\), which of the following is the mass percent of chloride in the original mixture, along with the correct justification for heating to constant mass?

A student determines the mass percent of chloride in an unknown solid mixture containing a soluble chloride salt and an inert, non-chloride water-soluble compound. The student dissolves a \(1.000\text{ g}\) sample of the mixture in distilled water and adds an excess of \(0.20\text{ M AgNO}_3\text{(aq)}\) to precipitate all chloride ions as \(\text{AgCl(s)}\). The precipitate is collected on filter paper in a crucible and heated repeatedly in an oven to dry it. The recorded data are shown in the table below.

| Measurement | Mass (g) |
|---|---|
| Mass of unknown solid mixture sample | \(1.000\) |
| Mass of empty crucible and filter paper | \(21.500\) |
| Mass of crucible, filter paper, and precipitate after 1st heating | \(23.220\) |
| Mass of crucible, filter paper, and precipitate after 2nd heating | \(22.950\) |
| Mass of crucible, filter paper, and precipitate after 3rd heating | \(22.933\) |
| Mass of crucible, filter paper, and precipitate after 4th heating | \(22.933\) |

Given that the molar mass of \(\text{AgCl}\) is \(143.3\text{ g/mol}\) and the atomic mass of \(\text{Cl}\) is \(35.45\text{ g/mol}\), which of the following is the mass percent of chloride in the original mixture, along with the correct justification for heating to constant mass?

- **A.** \(35.5\%\), because heating to constant mass ensures that all retained water is evaporated, preventing an overestimation of the precipitate mass and chloride content.
- **B.** \(35.5\%\), because repeated heating thermally decomposes excess adsorbed \(\text{AgNO}_3\), preventing an underestimation of the chloride content.
- **C.** \(42.5\%\), because only the mass after the first heating should be used to prevent loss of product caused by the thermal decomposition of \(\text{AgCl(s)}\).
- **D.** \(58.4\%\), because the moles of collected \(\text{AgCl(s)}\) must be converted to the mass of \(\text{NaCl}\) rather than the mass of elemental chloride.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/121489/*