Final answer:
To find the percent by mass of oxygen in the compound, divide the mass of oxygen by the mass of the compound and multiply by 100.
Step-by-step explanation:
To find the percent by mass of oxygen in the unknown compound, we need to determine the mass of oxygen in the compound and divide it by the mass of the compound. We are given that the sample of the unknown compound weighs 25.3g and contains 0.8g of oxygen.
To find the percent by mass of oxygen, we use the formula:
Percent by mass of oxygen = (Mass of oxygen / Mass of compound) × 100
Substituting the given values into the formula:
Percent by mass of oxygen = (0.8g / 25.3g) × 100 ≈ 3.16%