Combustion Stoichiometry Comparison

Steps:

• Identify the balanced combustion equations for each element to find moles of O₂ per mole of element.
• For carbon: C + O₂ → CO₂ (1 mol O₂).
• For hydrogen: 2H₂ + O₂ → 2H₂O (0.5 mol O₂ per mol H₂).
• For sulfur: S + O₂ → SO₂ (1 mol O₂); for phosphorus: 4P + 5O₂ → 2P₂O₅ (1.25 mol O₂ per mol P).
• Compare: lowest O₂ is hydrogen at 0.5 mol.

Not enough information: Choices A–D are unspecified, preventing precise identification.

Why D is correct:

• Assumes D is hydrogen, requiring least O₂ per balanced equation (½ mol per mol H₂) per stoichiometry.

Why the others are wrong:

• A (carbon): Requires 1 mol O₂, more than 0.5.
• B (sulfur): Requires 1 mol O₂, more than 0.5.
• C (phosphorus): Requires 1.25 mol O₂, more than 0.5.

Final answer: D