test for gases

• How to test the presence of Hydrogen

  • Add a lit splint to the gas.
  • If a squeaky pop is observed, Hydrogen gas is present.

  
• How to test the presence of Oxygen

  • Add a GLOWING SPLINT to the gas.
  • If the glowing splint RELIGHTS, Oxygen is present.

  
• How to test the presence of Carbon Dioxide

  • Bubble the gas through LIMEWATER.
  • If the limewater turns CLOUDY, the gas is Carbon Dioxide.

  
• How to test for Chlorine

  • Add DAMP BLUE LITMUS PAPER to the gas.
  • If the litmus paper BLEACHES WHITE, Chlorine is present.

  
• density


  number of particles in a given space
• gas less dense than air rises.
• Balloons that float

  • Contain helium which is less dense than air
• Balloons that fall to the ground

  • Contain mostly carbon dioxide which is more dense than air
• Upward delivery/downward displacement 


  Used to collect gases less dense than air like hydrogen gas (H2) and ammonia (NH3).
• Upwards delivery:

  • Pour HCI into conical flask
  • put magnesium strips into the conical flask
  • place delivery tube on the conical flask
  • Place a test tube over the delivery tube
  • collect hydrogen gas produced for 20s

  A) test tube

  B) delivery tube

  C) conical flask

  
• Downward delivery/upward displacement


  Used to collect gases more dense than air like carbon dioxide (CO2) and chlorine gas (Cl2).
• Downwards delivery:

  • Pour HCI into conical flask
  • Add spatulas of marble chips into the HCI
  • place delivery tube over the conical flask
  • Pass the carbon dioxide produced into the test tube

  A) delivery tube

  B) conical flask

  C) test tube

  
• Over water


  Used to collect gases with unknown density, wont work for gases that are soluble in water, such as ammonia (NH3).
• Over water method:

  • pour HCI and put magnesium into the conical flask
  • put delivery tube onto the conical flask
  • put the end of the delivery tube into a beaker filled with water.
  • put the test tube over the end of the delivery tube to collect the hydrogen gas.

  A) delivery tube

  B) conical flask

  C) test tube

  D) beaker

  
• Gas syringe method


  Used to collect gases with unknown solubility and density, also measures the volume of a gas.
• Gas syringe method:

  • connect the end of delivery tube and gas syringe
  • Put HCI and calcium carbonate chips into the conical flask
  • place the delivery tube onto the conical flask.
  • Let the carbon dioxide (CO2) to be produced into the gas syringe.

  A) conical flask

  B) delivery tube

  C) gas syringe

  
• Gas syringe equation:

  CaCO3 (S) + 2 HCI (AQ) --> CaCl2 (AQ) + H2O (L) + CO2 (G)
• (S)

  Solid
• (L)

  liquid
• (G)

  gas
• (AQ)

  Aqueous
• If the Gas syringe equation happens in a beaker, then the mass will decrease, because the gas will escape and the pH will increase as neutralisation from 2pH to 7pH.
• White anhydrous copper(II) sulphate turns blue in the presence of water.
• When an acid reacts with a metal, the products are a salt and hydrogen.