Final answer:
The theoretical percent sulfate in alum can be calculated using the formula mass of the compound. The molar mass of each element in the compound is multiplied by the number of atoms, and then the molar mass of the sulfate is divided by the formula mass of alum and multiplied by 100 to find the percent sulfate.
Step-by-step explanation:
The theoretical percent sulfate in alum can be calculated using the formula mass of the compound. The formula for alum is KAl(SO4)2 • 12H2O. To calculate the formula mass, you need to find the molar mass of each element and multiply it by the number of atoms in the compound. In this case, the molar mass of potassium (K) is 39.10 g/mol, the molar mass of aluminum (Al) is 26.98 g/mol, the molar mass of sulfur (S) is 32.07 g/mol, and the molar mass of oxygen (O) is 16.00 g/mol. The molar mass of water (H2O) is 18.02 g/mol. So, the formula mass of alum is:
(39.10 g/mol) + (26.98 g/mol) + 2(32.07 g/mol) + (4 x 16.00 g/mol) + 12(18.02 g/mol) = 474.39 g/mol
To find the theoretical percent sulfate, divide the molar mass of the sulfate (96.06 g/mol) by the formula mass of alum and multiply by 100:
(96.06 g/mol / 474.39 g/mol) x 100 = 20.27%