This problem comes from the open stax chemistry textbook. Average atomic weight were used from the periodic table found on ptable.com
Problem 3.8 Chemistry, 2nd edition Open Stax.
9. Which contains the greatest mass of oxygen: 0.75 mol of ethanol (C2H5OH), 0.60 mol of formic acid (HCO2H), or 1.0 mol of water (H2O). Explain why.