Answer:
The empirical formula is Al2Se3
Explanation:
<u>Step 1:</u> Data given
Mass of the sample of aluminium = 7.300 grams
Mass of the compound = 39.35 grams
Molar mass of aluminium = 26.98 g/mol
Molar mass of selenium = 78.96 g/mol
<u>Step 2:</u> Calculate mass of selenium
Mass of selenium = mass of compound - mass of aluminium
Mass of selenium = 39.35 - 7.3 = 32.05 grams
<u>
Step 3:</u> Calculate moles of Al
Moles Al = Mass Al/ Molar mass Al
Moles Al = 7.300 grams / 26.98 g/mol
Moles Al = 0.2706 moles
<u>Step 4:</u> Calculate moles of Se
Moles Se = Mass Se / Molar mass Se
Moles Se =32.05 g / 78.96 g/mol
Moles Se = 0.4059 moles
<u>Step 5</u>: Divide through the smallest amount of mol
Aluminium: 0.2706 / 0.2706 = 1
Selenium: 0.4059/0.2706 = 1.5
This means for each mol aluminium, we have 1.5 moles of selenium
For each 2 moles of aluminium, we have 3 moles of selenium
The empirical formula is Al2Se3
This is aluminium(III) selenide.
