How many formula units are in a sample of rust, Fe₂O₃ that has a mass of 5.0 g?

Question

Quizplus · Accepted Answer

The first step is to determine the molar mass of the compound: Fe = 1 mol x 55.85 g/mol = 55.85 g/mol S = 13 mol x 32.07 g/mol = 416.91 g/mol O = 1 mol x 16.00 g/mol = 16.00 g/mol Total molar mass = 488.76 g/mol Next, we can use the molar mass to convert the mass of the sample to the number of moles: 5.0 g Fe₂O₃ x (1 mol / 488.76 g) = 0.0102 mol Finally, we can use the coefficients in the chemical formula to determine the number of formula units: Fe₂O₃ = Fe1S1O1S1 x 12 + Fe1S1O1S1 x 13 = 25 formula units Number of formula units = 25 x 0.0102 mol = 0.255 formula units Since we cannot have a fractional number of formula units, we need to round to the nearest whole number. Therefore, the answer is 1.9 × 10^22 formula units, which is choice C.

How Many Formula Units Are in a Sample of Rust