Stoichiometric mass ratio from decomposition equation Steps:

• Balanced equation: 2Mg(NO₃)₂ → 2MgO + 4NO₂ + O₂ (white solid MgO; gases NO₂ and O₂).
• X is O₂ (16 g per mole Mg(NO₃)₂); Y is NO₂ (92 g per mole Mg(NO₃)₂).
• Mass X released = (½) × 32 = 16 g; mass Y released = 2 × 46 = 92 g.
• Ratio (mass X / mass Y) = 16 / 92 ≈ 0.174.

Why A is correct:

• Stoichiometry yields ½ mole O₂ per 2 moles NO₂, so mass ratio O₂:NO₂ = 16:92 = 0.174 by molar masses.

Why the others are wrong:

• B: Assumes NO (molar mass 30) instead of NO₂, giving 16/60 = 0.267.
• C: Uses 1 mole O₂ with 2 moles NO₂ (unbalanced), giving 32/92 ≈ 0.348.
• D: Inverted partial ratio, like 92/32 ≈ 2.88 adjusted wrongly to 3.43.

Final answer: A