How is ethene collected in the dehydration of ethanol?

• A. By displacement of water
• B. By distillation
• C. By filtration
• D. By precipitation

Answer: (A)

Gas collection by water displacement is used for gases that don’t dissolve in water and don’t react with it. Ethene produced when ethanol is dehydrated is a dry gas that isn’t soluble in water, so it can be captured by collecting the gas over water. The ethene bubbles out and pushes the water out of an inverted container, giving you the collected gas. The other options aren’t about gathering a gas: distillation separates liquids by boiling points, filtration removes solids, and precipitation forms a solid from solution.