C8 Chemical Analysis

• Testing for Hydrogen:

  • Hold a lit splint at the open end of a test tube containing a gas.
  • If the gas is hydrogen, a squeaky pop sound will be produced.
  • The noise is generated because hydrogen burns rapidly in the presence of oxygen to give water (H₂O)
• Testing for Oxygen:

  • Insert a glowing splint into a test tube containing gas.
  • If the gas is oxygen, the splint will relight
• Testing for Carbon Dioxide:

  • Bubble through or shake carbon dioxide with lime water (calcium hydroxide) in a test tube.
  • The solution will turn from clear to cloudy
• Testing for Chlorine:

  • Insert damp litmus paper into a test tube containing a gas.
  • If the gas is chlorine, the litmus paper will bleach and change color from red to white
• Paper Chromatography:

  • Process that separates a mixture into its different components
  • Solvent is the mobile phase, paper is the stationary phase
  • Substances are carried by the mobile phase and move through the stationary phase
  • The most soluble substance will move furthest up the paper
  • Rf value = distance traveled by substance / distance traveled by solvent
• Practical - Paper Chromatography:

  1. Use a pencil to draw a horizontal line near the bottom of the chromatography paper.

  2. Place samples of known food colorings (A-D) alongside an unknown substance (X) on the start line.

  3. Put the paper in a beaker with a small volume of solvent.

  4. Wait for the solvent to travel near the top of the paper.

  5. Compare the spots produced by the unknown substance with those produced by A-D to identify the unknown substance
• Pure Substances:

  • Pure substances contain only one substance.
  • They have exact and specific melting and boiling points.
  • Impurities increase the boiling point and decrease the melting point, leading to a wider range of temperature for melting.
  • Formulations are mixtures of chemicals designed to create useful products