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title: "A student determines the mass percentage of copper in an impure brass alloy that contains copper, zinc, and an insoluble inert silicate impurity. The student measures a sample of the alloy, dissolves the metallic components in acid, filters and dries the insoluble impurity, and quantitatively precipitates all dissolved copper as pure, dry copper(II) oxide, \\(\\text{CuO(s)}\\). The data collected during the experiment are shown in the table below.  | Measurement | Mass (g) | |—|—| | Mass of empty weighing dish | \\(12.50\\) | | Mass of weighing dish \\(+\\) brass sample | \\(16.50\\) | | Mass of dry filter paper | \\(0.80\\) | | Mass of filter paper \\(+\\) dried insoluble impurity | \\(1.60\\) | | Mass of empty watch glass | \\(22.00\\) | | Mass of watch glass \\(+\\) dried \\(\\text{CuO(s)}\\) | \\(25.00\\) |  Given that the molar mass of \\(\\text{Cu}\\) is \\(64.0\\text{ g/mol}\\) and the molar mass of \\(\\text{CuO}\\) is \\(80.0\\text{ g/mol}\\), what is the mass percentage of copper in the original brass sample?"
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url: "https://nerd-notes.com/ubq/119735/"
date_modified: "2026-08-21T08:12:11+00:00"
---

# A student determines the mass percentage of copper in an impure brass alloy that contains copper, zinc, and an insoluble inert silicate impurity. The student measures a sample of the alloy, dissolves the metallic components in acid, filters and dries the insoluble impurity, and quantitatively precipitates all dissolved copper as pure, dry copper(II) oxide, \(\text{CuO(s)}\). The data collected during the experiment are shown in the table below.

| Measurement | Mass (g) |
|—|—|
| Mass of empty weighing dish | \(12.50\) |
| Mass of weighing dish \(+\) brass sample | \(16.50\) |
| Mass of dry filter paper | \(0.80\) |
| Mass of filter paper \(+\) dried insoluble impurity | \(1.60\) |
| Mass of empty watch glass | \(22.00\) |
| Mass of watch glass \(+\) dried \(\text{CuO(s)}\) | \(25.00\) |

Given that the molar mass of \(\text{Cu}\) is \(64.0\text{ g/mol}\) and the molar mass of \(\text{CuO}\) is \(80.0\text{ g/mol}\), what is the mass percentage of copper in the original brass sample?

A student determines the mass percentage of copper in an impure brass alloy that contains copper, zinc, and an insoluble inert silicate impurity. The student measures a sample of the alloy, dissolves the metallic components in acid, filters and dries the insoluble impurity, and quantitatively precipitates all dissolved copper as pure, dry copper(II) oxide, \(\text{CuO(s)}\). The data collected during the experiment are shown in the table below.

| Measurement | Mass (g) |
|---|---|
| Mass of empty weighing dish | \(12.50\) |
| Mass of weighing dish \(+\) brass sample | \(16.50\) |
| Mass of dry filter paper | \(0.80\) |
| Mass of filter paper \(+\) dried insoluble impurity | \(1.60\) |
| Mass of empty watch glass | \(22.00\) |
| Mass of watch glass \(+\) dried \(\text{CuO(s)}\) | \(25.00\) |

Given that the molar mass of \(\text{Cu}\) is \(64.0\text{ g/mol}\) and the molar mass of \(\text{CuO}\) is \(80.0\text{ g/mol}\), what is the mass percentage of copper in the original brass sample?

- **A.** \(15.0\%\)
- **B.** \(20.0\%\)
- **C.** \(48.0\%\)
- **D.** \(60.0\%\)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119735/*