A compound contains 40% carbon, 6.67% hydrogen, and 53.33% oxygen by mass. What is its empirical formula? [C = 12, H = 1, O = 16]

Dividing each percentage by the respective atomic mass: C = 40/12 = 3.33; H = 6.67/1 = 6.67; O = 53.33/16 = 3.33. Dividing by the smallest ratio (3.33): C = 1, H = 2, O = 1, giving the empirical formula CH₂O. Option B is the molecular formula of acetic acid and option C has incorrect hydrogen count.