We’re being asked to** ****determine the number of atoms of zinc in a fitting** containing **37.0 % by mass Zn**.

We know that the fitting is a common brass alloy composed of copper, Cu and Zinc, Zn.

And to do that we're going to do the following steps:

*Step 1: Solve for mass of the common brass fitting (solution) using the volume and *

*density of the fitting.*

**volume solution (density) → mass solution**

*Step 2: Solve for mass of Zinc using the mass percent formula shown below:*

$\overline{){\mathbf{mass}}{\mathbf{}}{\mathbf{percent}}{\mathbf{=}}\frac{\mathbf{mass}\mathbf{}\mathbf{component}}{\mathbf{total}\mathbf{}\mathbf{mass}}{\mathbf{\times}}{\mathbf{100}}}$

Since we are dealing with an **alloy (solid solution)**, we can rewrite the equation as:

$\overline{){\mathbf{\%}}{\mathbf{}}{\mathbf{mass}}{\mathbf{=}}\frac{\mathbf{mass}\mathbf{}\mathbf{solute}}{\mathbf{mass}\mathbf{}\mathbf{solution}}{\mathbf{\times}}{\mathbf{100}}}$

*Step 3: Solve for moles of Zn in fitting and # of atoms of Zn using Avogadro's number*

Common brass is a copper and zinc alloy containing 37.0% zinc by mass and having a density of 8.48 g/cm^{3}. A fitting composed of common brass has a total volume of 120.5 cm^{3} .

How many atoms of zinc does the fitting contain?

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Our tutors have indicated that to solve this problem you will need to apply the Mass Percent concept. You can view video lessons to learn Mass Percent. Or if you need more Mass Percent practice, you can also practice Mass Percent practice problems.