Question

How many formula units are in 9.3 g of alumina (Al2O3)?
Answer in units of formula units.

Answer 1

Answer:

5.5 × 10²² formula units Al₂O₃

General Formulas and Concepts:

Chemistry - Stoichiometry

• Reading a Periodic Table
• Dimensional Analysis
• Avogadro's Number - 6.022 × 10²³ atoms, molecules, formula units, etc.

Explanation:

Step 1: Define

9.3 g Al₂O₃

Step 2: Define conversions

Avogadro's Number

Molar Mass of Al - 26.98 g/mol

Molar Mass of O - 16.00 g/mol

Molar Mass of Al₂O₃ - 2(26.98) + 3(16.00) = 101.96 g/mol

Step 3: Convert

$9.3 \ g \ Al_2O_3(\frac{1 \ mol \ Al_2O_3}{101.96 \ g \ Al_2O_3} )(\frac{6.022 \cdot 10^{23} \ formula \ units \ Al_2O_3}{1 \ mol \ Al_2O_3} )$ = 5.4928 × 10²² formula units Al₂O₃

Step 4: Check

We are given 2 sig figs. Follow sig fig rules.

5.4928 × 10²² formula units Al₂O₃ ≈ 5.5 × 10²² formula units Al₂O₃