How Do You Collect Hydrogen & Sulphur Di Oxide Gas-By Upward Or Downward Collection Of Air ?
Hydrogen is less dense than air so you would collect it by downward displacement of air. SO2 is denser than air and so you would collect it by upward displacement of air. I can think of no gas that is denser than water – so all gases are collected by downward displacement of water. But the main point here is that SO2 is both soluble in and reacts with water, so you would (after suitable drying) collect it by upward displacement of air. It is fine to collect hydrogen (which has a very low solubility) over water.
