To determine the percentage of oxygen by mass in FeCr2O4, we need to calculate the molar mass of the compound and then find the mass of oxygen in one mole of the compound.
The molar mass of FeCr2O4 can be calculated by summing the atomic masses of its constituent elements: iron (Fe), chromium (Cr), and oxygen (O). The atomic masses (rounded to two decimal places) are:
Fe: 55.85 g/mol Cr: 52.00 g/mol O: 16.00 g/mol
FeCr2O4 contains 2 moles of chromium, so we calculate the molar mass as follows:
Molar mass of FeCr2O4 = (1 × molar mass of Fe) + (2 × molar mass of Cr) + (4 × molar mass of O)
Molar mass of FeCr2O4 = (1 × 55.85 g/mol) + (2 × 52.00 g/mol) + (4 × 16.00 g/mol)
Molar mass of FeCr2O4 = 55.85 g/mol + 104.00 g/mol + 64.00 g/mol
Molar mass of FeCr2O4 = 223.85 g/mol
The mass of oxygen in one mole of FeCr2O4 is equal to the product of the molar mass of oxygen and the number of moles of oxygen in the compound. Since there are four moles of oxygen in FeCr2O4, we calculate the mass of oxygen as follows:
Mass of oxygen = 4 × molar mass of O
Mass of oxygen = 4 × 16.00 g/mol
Mass of oxygen = 64.00 g
Finally, to calculate the percentage of oxygen by mass, we divide the mass of oxygen by the molar mass of FeCr2O4 and multiply by 100:
Percentage of oxygen by mass = (mass of oxygen / molar mass of FeCr2O4) × 100
Percentage of oxygen by mass = (64.00 g / 223.85 g/mol) × 100
Percentage of oxygen by mass ≈ 28.60%
Therefore, the percent of oxygen by mass in FeCr2O4 is approximately 28.60%.