To determine the percent of oxygen by mass in a pure sample of FeCr2O4, we need to calculate the mass of oxygen relative to the total mass of the compound.
The compound FeCr2O4 consists of one iron atom (Fe), two chromium atoms (Cr), and four oxygen atoms (O). To calculate the percent of oxygen by mass, we divide the mass of oxygen by the total mass of the compound and multiply by 100.
To proceed, we need to know the atomic masses of iron (Fe), chromium (Cr), and oxygen (O). The atomic masses are approximately:
Fe: 55.845 atomic mass units (u) Cr: 51.9961 u O: 15.999 u
Now, let's calculate the mass of oxygen in the compound:
Mass of oxygen = 4 atoms of O * 15.999 u/atom = 63.996 u
Next, we calculate the total mass of the compound:
Total mass of FeCr2O4 = (1 atom of Fe * 55.845 u) + (2 atoms of Cr * 51.9961 u) + (4 atoms of O * 15.999 u) = 231.8342 u
Finally, we calculate the percent of oxygen by mass:
Percent of oxygen by mass = (Mass of oxygen / Total mass of FeCr2O4) * 100 Percent of oxygen by mass = (63.996 u / 231.8342 u) * 100 ≈ 27.61%
Therefore, the percent of oxygen by mass in a pure sample of FeCr2O4 is approximately 27.61%.