Question

Aluminum oxide (Al2O3) occurs in nature as a mineral called corundum, which is noted for its hardness and resis- tance to attack by acids. Its density is 3.97 g cm23. Calculate the number of atoms of aluminum in 15.0 cm3 corundum.

Answer 1

7.03×10²³ atoms of Al

Step-by-step explanation:

Corundum density = 3.97g/cm³

Corundum = Al₂O₃. Then, you have 2 moles of Al and 3 moles of O in 1 mol of the compound.

Let's determine the mass of corundum, by density

Corundum density = Corundum mass / Corundum volume

3.97 g/cm³ = Corundum mass / 15cm³

3.97 g/cm³ . 15cm³ = Corundum mass →59.55 g

Now, let's find out how many moles are in that mass of corundum

1 mol of Al₂O₃ weighs 101.96 g/mol

Then, 101.96 grams of oxide have 2 moles of Al

59.55 g of oxide, will have (59.55 .2)/101.96 = 1.17 moles

Now, we can know the quantity of atoms, by this rule of three

1 mol has NA atoms (6.02×10²³)

1.17 moles will have (1.17 . NA) = 7.03×10²³ atoms of Al