Calculate the mass fractions for each of the elements in the aluminum sulfate substance.

Decision:
1. Aluminum sulfate has the following chemical formula – Al2 (SO4) 3. Let’s find its molecular weight:
27 * 2 + 32 * 3 + 16 * 12 = 342;
1. Let’s find the mass fraction of aluminum in the substance:
27 * 2/342 = 54/342 = 0.1579 (15.79%);
1. Let’s find the mass fraction of sulfur in the substance:
32 * 3/342 = 96/342 = 0.2807 (28.07%);
1. Let’s find the mass fraction of oxygen in the substance:
16 * 12/342 = 192/342 = 0.5614 (56.14%);
Answer: the mass fraction of aluminum is 15.79%, the mass fraction of sulfur is 28.07%, the mass fraction of oxygen is 56.14%.