8.2 Identification of common gases

• Hydrogen produces a loud "pop" sound when ignited with a burning splint.


  True
• Carbon dioxide turns limewater cloudy
• What are the key properties of gases used to identify them?

  Colour, odour, flammability, acidity/alkalinity
• Hydrogen sulfide has a distinct smell like rotten eggs
• The "pop" sound in the hydrogen test is caused by rapid combustion with oxygen.

  True
• What is the test for hydrogen gas using a burning splint?

  Loud "pop" sound
• Hydrogen sulfide smells like rotten eggs.


  True
• What sound is produced when hydrogen reacts with a burning splint?

  Loud "pop" sound
• What sound is produced when testing for hydrogen gas with a burning splint?

  "Pop"
• What happens to a glowing wooden splint when testing for oxygen gas?

  It bursts into flame
• What happens when oxygen is tested with a glowing splint?

  Splint bursts into flame
• What is the observation when chlorine is tested with damp blue litmus paper?

  Turns red, then bleaches white
• Order the steps for testing oxygen gas.

  1️⃣ Prepare a test tube containing oxygen gas

  2️⃣ Bring a glowing wooden splint near the gas

  3️⃣ Observe that the splint bursts into flame
• Chlorine gas has a greenish-yellow colour.


  True
• What sound is heard when a burning splint is brought to hydrogen gas?

  Loud "pop" sound
• What is the test for oxygen gas using a glowing splint?

  Splint bursts into flame
• What happens to damp blue litmus paper when exposed to chlorine gas?

  Turns red, then bleaches white
• Match the gas with its test and observation:

  Oxygen ↔️ Glowing splint, splint bursts into flame

  Hydrogen ↔️ Burning splint, loud "pop" sound

  Chlorine ↔️ Damp blue litmus paper, turns red then bleaches white

  Carbon Dioxide ↔️ Limewater, turns cloudy
• Chlorine gas is greenish-yellow in colour.


  True
• The "pop" sound in the hydrogen test is caused by the rapid combustion of hydrogen with oxygen in the air.


  True
• The glowing splint reignites because oxygen supports combustion
• What does limewater turn when carbon dioxide is bubbled through it?

  Cloudy
• Chlorine gas turns damp blue litmus paper red before bleaching it white.

  True
• Ammonia is an alkaline gas that reacts with the moisture in the litmus paper
• Why is it important to wear protective gloves and eyewear in the lab?

  To shield skin and eyes
• Oxygen gas relights a glowing splint, causing it to burst into flame.


  True
• Order the steps for testing gases based on the information in the table.

  1️⃣ Bring a burning splint to the mouth of the test tube for hydrogen

  2️⃣ Bring a glowing wooden splint near the gas for oxygen

  3️⃣ Bring damp blue litmus paper near the gas for chlorine

  4️⃣ Bubble the gas through limewater for carbon dioxide
• Match the gas property with its identifying characteristic:

  Odour ↔️ Distinct smells

  Colour ↔️ Direct visual observation

  Flammability ↔️ Reacts with a burning splint

  Acidity/Alkalinity ↔️ Changes litmus paper
• Oxygen supports combustion by enabling the rapid oxidation of wood.
• To test for oxygen, a glowing wooden splint is brought near the gas
• What chemical compound is formed when carbon dioxide reacts with limewater?

  Calcium carbonate
• The reaction between carbon dioxide and limewater turns the solution cloudy


  True
• Chlorine's acidic nature is indicated by litmus paper turning red
• What happens to damp red litmus paper when exposed to ammonia gas?

  Turns blue
• Ammonia gas is alkaline and turns damp red litmus paper blue


  True
• Sulfur dioxide reduces dichromate ions to chromium ions, causing the solution to turn green
• Why should a fume hood be used when handling hazardous vapors in a lab?

  To prevent inhalation
• Match the gas with its identifying test and observation:

  Oxygen ↔️ Relights a glowing splint ||| Splint bursts into flame

  Carbon Dioxide ↔️ Bubble through limewater ||| Limewater turns cloudy

  Ammonia ↔️ Bring damp red litmus paper ||| Turns blue
• Oxygen supports combustion because it enables the glowing embers to burst into flames.


  True
• The white precipitate formed in the carbon dioxide test is calcium carbonate