In an experiment using ethanol, what is a better apparatus arrangement and why?

• A. Cover the apparatus with a lid, because ethanol is volatile.
• B. Leave the lid off to increase airflow.
• C. Heat strongly to remove ethanol quickly.
• D. Use a wider vessel to reduce pressure.

Answer: (A)

Ethanol evaporates very readily, so you want to minimize its loss and the amount of vapors in the air. Covering the apparatus with a lid helps trap the ethanol vapors and keep more solvent in the liquid, reducing evaporation and limiting exposure to flammable vapors. Leaving the lid off would allow more evaporation and more vapors to escape, heating strongly to remove ethanol quickly is dangerous and wasteful, and a wider vessel increases surface area, which would actually boost evaporation rather than reduce it. So, using a lid is the safer, more effective choice for this situation.