Reaction ring position from gas diffusion rates

Steps:

• Ethylamine (C₂H₅NH₂, molar mass 45 g/mol) and HCl (molar mass 36.5 g/mol) react: C₂H₅NH₂(g) + HCl(g) → C₂H₅NH₃Cl(s).
• Solid forms where gases meet in the tube.
• Diffusion rate follows Graham's law: lighter HCl diffuses faster than heavier ethylamine.
• Ring forms closer to ethylamine end, as HCl travels farther before reacting.

Why A is correct:

• A marks the position near the ethylamine source, matching slower diffusion of heavier gas per Graham's law.

Why the others are wrong:

• B: Midway would occur if gases had equal diffusion rates.
• C: Near HCl end fits lighter amine like ammonia, not heavier ethylamine.
• D: At ethylamine end ignores HCl diffusion entirely.

Final answer: A