The table below shows some information for four different elements.

\begin{tabular}{|c|c|c|}
\hline Element & Classification & \begin{tabular}{l}
Density \\
[tex]$\left( g / cm ^3 \right)$[/tex]
\end{tabular} \\
\hline barium [tex]$( Ba )$[/tex] & metal & 3.6 \\
\hline beryllium [tex]$( Be )$[/tex] & metal & 1.8 \\
\hline chromium [tex]$( Cr )$[/tex] & metal & 7.2 \\
\hline phosphorus [tex]$( P )$[/tex] & nonmetal & 1.8 \\
\hline
\end{tabular}

A cube of an unknown element has a shiny, silvery color. The side of the cube measures 2.0 cm and the cube has a mass of 14.56 g.

Based on the information in the table, which element makes up the cube?

A. barium
B. beryllium
C. chromium
D. phosphorus



Answer :

Let's solve this step-by-step:

1. Given Information:

- The side of the cube is 2.0 cm.
- The mass of the cube is 14.56 g.
- We need to determine the element based on the given densities and classification.

2. Calculate the Volume of the Cube:

The volume (V) of a cube can be calculated using the formula:
[tex]\[ V = \text{side length}^3 \][/tex]
Given the side length is 2.0 cm, we calculate:
[tex]\[ V = 2.0 \, \text{cm}^3 = 2.0 \times 2.0 \times 2.0 = 8.0 \, \text{cm}^3 \][/tex]

3. Calculate the Density of the Cube:

The density (ρ) of a substance is defined as its mass (m) divided by its volume (V):
[tex]\[ \rho = \frac{\text{mass}}{\text{volume}} \][/tex]
Given the mass is 14.56 g and the volume is 8.0 cm³, we calculate:
[tex]\[ \rho = \frac{14.56 \, \text{g}}{8.0 \, \text{cm}^3} = 1.82 \, \text{g/cm}^3 \][/tex]

4. Compare the Density to Known Densities:

We are given the following densities for different elements:
[tex]\[ \begin{aligned} &\text{Barium (Ba)}: 3.6 \, \text{g/cm}^3 \\ &\text{Beryllium (Be)}: 1.8 \, \text{g/cm}^3 \\ &\text{Chromium (Cr)}: 7.2 \, \text{g/cm}^3 \\ &\text{Phosphorus (P)}: 1.8 \, \text{g/cm}^3 \\ \end{aligned} \][/tex]
The calculated density of the cube (1.82 g/cm³) doesn't exactly match any of the given densities. However, it is closest to the density of beryllium (1.8 g/cm³) and phosphorus (1.8 g/cm³).

5. Account for Classification and Appearance:

- The unknown element cube is described as having a shiny, silvery color.
- Phosphorus is a nonmetal and typically not shiny and silvery. In contrast, beryllium is a metal and matches the description of being shiny and silvery.

6. Conclusion:

Given the density of the cube is closest to 1.8 g/cm³ and the appearance described fits that of a metal, the cube is most likely made of beryllium (Be).

Thus, the element that makes up the cube is:

B. Beryllium (Be)