unit 1.2

• In the method of gas collection using water displacement, gases must be insoluble or slightly soluble in water
• Density does not affect water displacement
• Examples of gases that can be collected using water displacement include hydrogen, oxygen, and carbon dioxide
• Method of gas collection: Water displacement

  
• Gases with a mass of molecule greater than 30 are denser than air
• Examples of gases denser than air include chlorine, hydrogen chloride, and sulfur dioxide
• In the method of gas collection using downward delivery, gases can be insoluble or slightly soluble in water
• Collection method: downward delivery

  
• for upward delivery: Gases can be soluble or insoluble
• For upwards delivery: Gases with a mass less than 30 are less dense than air
• Examples of gases denser than air include ammonia
• Method of collection: upwards delivery

  
• Concentrated sulfuric acid is not suitable for drying gases that react with sulfuric acid, such as ammonia
• Concentrated sulfuric acid is suitable for drying most gases, including chlorine and hydrogen chloride
• Quicklime (calcium oxide) absorbs moisture and carbon dioxide from the gas, so it needs to be freshly heated beforehand
• Quicklime (calcium oxide) is not suitable as a drying agent for gases that react with it, such as carbon dioxide
• Quicklime (calcium oxide) is suitable for drying ammonia