Answer:
The answer to your question is empirical formula Al₃O₉S
Step-by-step explanation:
Data
Al = 31.5 %
O = 56.1 %
S = 12.4 %
Process
1.- Look for the atomic masses of the elements
Al = 27 g
O = 16
S = 32
2.- Represent the percentages as grams
Al = 31.5 g
O = 56.1 g
S = 12.4 g
3.- Convert these masses to moles
27 g of Al ----------------- 1 mol
31.5 g ---------------------- x
x = 1.17 moles
16 g of O ---------------- 1 mol
56.1 g of O ------------- x
x = 3.5 mol
32 g of S --------------- 1 mol
12.4 g of S ------------- x
x = 0.39 moles
4.- Divide by the lowest number of moles
Al = 1.17 / 0.39 = 3
O = 3.5 / 0.39 = 8.9 ≈ 9
S = 0.39 / 0.39 = 1
5.- Write the empirical equation
Al₃O₉S