Determining CO₂ volume using reaction stoichiometry and RTP molar volume

Steps:

• Convert HCl volume to dm³ and calculate moles: assuming intended 250 cm³ = 0.25 dm³, moles HCl = 1.0 mol dm⁻³ × 0.25 dm³ = 0.25 mol.
• Apply stoichiometry from equation: 2 mol HCl produce 1 mol CO₂, so moles CO₂ = 0.25 mol / 2 = 0.125 mol.
• Recall molar volume at RTP: 1 mol gas occupies 24 dm³.
• Compute CO₂ volume: 0.125 mol × 24 dm³ mol⁻¹ = 3.0 dm³.

Why A is correct:

• Matches calculation from moles of limiting HCl, stoichiometric ratio (1:2 CO₂:HCl), and RTP molar volume law (24 dm³ mol⁻¹).

Why the others are wrong:

• B: Assumes 1:1 HCl:CO₂ ratio, doubling moles of CO₂ to 0.25 mol (6.0 dm³).
• C: Assumes incorrect 1:4 ratio or forgets to halve moles of CO₂.
• D: Assumes 1 full mol CO₂ regardless of HCl amount.

Final answer: A