Moles of oxygen atoms per gram of compound

Steps:

• Calculate moles of each compound in 1g: moles = 1 / relative formula mass (Mr).
• Determine oxygen atoms per formula unit: Al₂O₃ (3), CuSO₄ (4), H₂SO₄ (4), HNO₃ (3).
• Compute moles of O atoms: moles of compound × oxygen atoms per formula.
• Compare: Al₂O₃ (0.0294), CuSO₄ (0.05), H₂SO₄ (0.0408), HNO₃ (0.0476)—highest is HNO₃.

Why D is correct:

• HNO₃ has the lowest Mr (63) relative to its 3 O atoms, maximizing moles of O per gram via moles = mass / Mr.

Why the others are wrong:

• A: Al₂O₃'s high Mr (102) yields fewest moles of compound, thus fewest O atoms despite 3 O.
• B: CuSO₄'s 4 O atoms offset by low Mr (80), but still less O moles than HNO₃.
• C: H₂SO₄'s 4 O atoms hindered by higher Mr (98) than HNO₃, reducing O moles per gram.

Final answer: D