Determining oxygen atoms using composition and molar mass

Steps:

• Calculate oxygen mass in 100 g sample: 100 g - 40 g C - 6 g H = 54 g O.
• Scale to 90 g (1 mol compound): oxygen mass = (54/100) × 90 g = 48.6 g O.
• Compute moles of O: 48.6 g / 16 g/mol ≈ 3.04 mol.
• Round to nearest integer for formula: 3 oxygen atoms per molecule (consistent with C₃H₆O₃, molar mass 90 g/mol).

Why C is correct:

• Moles of oxygen per mole of compound ≈ 3, matching the molecular formula C₃H₆O₃ where oxygen mass fraction aligns with given data.

Why the others are wrong:

• A: 1 O would give 16 g O/mol, but calculated 48.6 g O/mol.
• B: 2 O would give 32 g O/mol, but calculated 48.6 g O/mol.
• D: 4 O would give 64 g O/mol, exceeding calculated 48.6 g O/mol.

Final answer: C