To find the unknown metal based on its mass and volume, we can calculate its density using the formula:
\[ \text{Density} = \frac{\text{Mass}}{\text{Volume}} \]
Given:
- Mass = \(21 , \text{grams}\)
- Volume = \(2 , \text{cm}^3\)
Now, substituting the values into the formula:
\[ \text{Density} = \frac{21 , \text{grams}}{2 , \text{cm}^3} = 10.5 , \text{grams/cm}^3 \]
Now, we can compare this density to the densities of the metals provided:
- Cobalt: \(8.9 , \text{g/cm}^3\)
- Silver: \(10.5 , \text{g/cm}^3\)
- Lead: \(11.3 , \text{g/cm}^3\)
- Platinum: \(21.4 , \text{g/cm}^3\)
- Chromium: \(7.2 , \text{g/cm}^3\)
The density of the unknown metal, calculated as \(10.5 , \text{g/cm}^3\), matches the density of silver.
Therefore, the unknown metal is silver.