C8- chemical analysis

• Why is obtaining pure substances important in chemistry?

  It ensures accurate chemical analysis
• How can we determine if a substance is pure?

  By testing its melting or boiling point
• What is a formulation?

  A mixture designed for a specific use
• What is chromatography used for?

  Separating substances in a mixture
• What is the stationary phase in chromatography?

  Special chromatography paper or filter paper
• What is the mobile phase in chromatography?

  Often just water that moves up the paper
• How do we measure the movement of substances in chromatography?

  From the starting line drawn in pencil
• What does RF value stand for in chromatography?

  Retention factor, a movement ratio
• What is the range of RF values?

  A number between zero and one
• How can we identify substances in a mixture using RF values?

  By comparing with known RF values
• How do we test for hydrogen gas?

  By holding a burning splint over it
• What happens when oxygen is tested with a glowing splint?

  It will relight the glowing splint
• What is the test for carbon dioxide?

  It turns lime water cloudy
• How does chlorine gas react with damp blue litmus paper?

  It bleaches the paper white
• What color flame does lithium produce in a flame test?

  Crimson flame
• What color flame does sodium produce in a flame test?

  Yellow flame
• What color flame does potassium produce in a flame test?

  Lilac flame
• What color flame does calcium produce in a flame test?

  Orange-red flame
• What color flame does copper produce in a flame test?

  Green flame
• How can we test for metals in solutions?

  By adding sodium hydroxide
• What precipitate do aluminium, calcium, and magnesium produce with sodium hydroxide?

  A white precipitate
• What happens to aluminium hydroxide when excess sodium hydroxide is added?

  It dissolves in excess sodium hydroxide
• What color precipitate do copper(II) ions form with sodium hydroxide?

  Blue precipitate
• What color precipitate do iron(II) ions form with sodium hydroxide?

  Green precipitate
• What color precipitate do iron(III) ions form with sodium hydroxide?

  Brown precipitate
• What do carbonates produce when they react with acids?

  Carbon dioxide gas
• How do we test for halide ions?

  By mixing with silver nitrate solution
• What precipitate is formed when chlorine ions are present?

  White precipitate of silver chloride
• What precipitate is formed when bromide ions are present?

  Cream precipitate of silver bromide
• What precipitate is formed when iodide ions are present?

  Yellow precipitate of silver iodide
• What happens when sulfate ions are mixed with barium chloride?

  A white precipitate is produced
• What are instrumental methods used for in chemical analysis?

  To determine substances accurately and quickly
• What is flame emission spectroscopy?

  A method to identify emitted wavelengths
• How does flame emission spectroscopy work?

  Light from a flame is analyzed for wavelengths
• What can be identified using an emission line spectrum?

  Metal ions based on emitted wavelengths
• What are the key chemical tests for identifying substances?

  • Hydrogen: Burning splint produces a pop
  • Oxygen: Glowing splint relights
  • Carbon dioxide: Turns lime water cloudy
  • Chlorine: Bleaches damp blue litmus paper
  • Flame tests for metals: Different colors for each metal
  • Precipitation reactions for ions: Specific precipitate colors
• What are the steps involved in chromatography?

  1. Draw a pencil line on chromatography paper
  2. Apply the mixture on the line
  3. Add the mobile phase (solvent)
  4. Allow the solvent to rise by capillary action
  5. Measure distances moved by solvent and substances
  6. Calculate RF values for identification