Final answer:
To calculate the mass of iron in a 10.0 gram sample of Iron (II) oxide, multiply the mass percent of iron by the sample mass. Then, to find the mass of oxygen in the same sample, subtract the mass of iron from the total sample mass.
Step-by-step explanation:
To find the mass of iron in a sample of Iron (II) oxide, we need to first determine the mass percent of iron in the compound.
Given that Iron (II) oxide is 77.8% iron by mass, we can assume that a 100 gram sample of Iron (II) oxide will contain 77.8 grams of iron.
Therefore, the mass of iron in a 10.0 gram sample of Iron (II) oxide can be calculated using the following equation:
Mass of iron = (mass percent of iron/100) * sample mass
Mass of iron = (77.8/100) * 10.0
Mass of iron = 7.78 grams
To calculate the mass of oxygen in the same sample, we can subtract the mass of iron from the total sample mass.
Mass of oxygen = sample mass - mass of iron = 10.0 - 7.78 = 2.22 grams