Density Exercise 2


2. Fill in the following table. Use the density table above to identify the substances.

ANSWERS ARE SHOWN IN GREEN in TABLE



WORKED OUT SOLUTION:

The first line of the table has been filled out. In the second line we are given a mass of 57.4 g and a volume of 6.84 cm3. We need to determine the density and the identity of the substance. First we calculate the density.

\(\displaystyle d\;=\;\frac{m}{V}\;=\;\frac{57.4\;g}{6.84\;cm^3}\;=\;\mathbf{8.39\;g\;cm^3}\)

We can determine the identity of the substance by looking at the table of densities. The identity is most likely copper.

In the third line of the table we are given a mass of 22.65 g and a density of 19.3 g/cm3. The identity of the substance is most likely gold. We need to find the volume.

\(\displaystyle V\;=\;\frac{mass}{density}\;=\;\frac{22.65\;g}{19.3\;g/cm^3}\;=\;\mathbf{1.17\;cm^3}\)

In the fourth line of the table, we have a mass of 625 mg and a density of 2.7 g/cm3. First we must convert 625 mg to grams. We have 0.625 g. The identity of the substance is aluminum. Next we find the volume.

\(\displaystyle V\;=\;\frac{mass}{density}\;=\;\frac{0.625\;g}{2.7\;g/cm^3}\;=\;\mathbf{0.23\;cm^3}\)

In the fifth line of the table we are given 5.00 L and 6.46 g. We need to calculate the density. First we convert 5.00 L to 5000 mL = 5000 cm3.

\(\displaystyle d\;=\;\frac{m}{V}\;=\;\frac{6.46\;g}{5000\;cm^3}\;=\;\mathbf{0.001292\;g\;cm^3}\)

Comparing the calculated density to the densities in the table the identity of our substance is most likely air.

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