Questions: What is the empirical formula of the compound with the following compositions: 20.2 percent Al, 79.8 percent Cl?

Solution Steps

Assume we have 100 grams of the compound. This means we have:

• 20.2 grams of Al
• 79.8 grams of Cl

To find the number of moles, use the formula:

\[ \text{moles} = \frac{\text{mass (g)}}{\text{molar mass (g/mol)}} \]

• Molar mass of Al = 26.98 g/mol
• Molar mass of Cl = 35.45 g/mol

Calculate moles of Al:

\[ \text{moles of Al} = \frac{20.2 \, \text{g}}{26.98 \, \text{g/mol}} \approx 0.7485 \, \text{mol} \]

Calculate moles of Cl:

\[ \text{moles of Cl} = \frac{79.8 \, \text{g}}{35.45 \, \text{g/mol}} \approx 2.2511 \, \text{mol} \]

Divide each mole value by the smallest number of moles calculated:

\[ \frac{0.7485}{0.7485} = 1 \]

\[ \frac{2.2511}{0.7485} \approx 3.007 \]

Since 3.007 is very close to 3, we can round it to 3.

Final Answer