chemical analysis

• What is a pure substance?

  Contains only one type of element or compound
• What are the melting and boiling points of pure water?

  Melts at 0°C and boils at 100°C
• What is a mixture?

  Contains two or more substances not chemically bonded
• How do mixtures behave in terms of melting and boiling points?

  They melt and boil over a range of temperatures
• What is a formulation?

  A mixture designed for a specific purpose
• Why are formulations important?

  They ensure correct dosage and improve performance
• What is chromatography?

  Used to separate and identify substances in mixtures
• What principle does chromatography work on?

  Substances move at different speeds in a solvent
• What are the steps in paper chromatography?

  1. Draw a pencil line on chromatography paper
  2. Place a small spot of mixture on the line
  3. Place paper in solvent (line above liquid)
  4. Solvent moves up, carrying substances at different speeds
• What is the stationary phase in chromatography?

  The paper that does not move
• What is the mobile phase in chromatography?

  The solvent that moves up the paper
• What is the Rf value in chromatography?

  A number used to identify substances
• How is the Rf value calculated?

  Rf = Distance moved by substance / Distance moved by solvent
• If a dye moves 4 cm and the solvent front moves 8 cm, what is the Rf value?

  0.5
• Why is chromatography used?

  To identify colors in food dyes and detect drugs
• What are the tests for gases and their positive results?

  • Hydrogen (H₂): Lit splint → Squeaky pop
  • Oxygen (O₂): Glowing splint → Relights
  • Carbon Dioxide (CO₂): Limewater → Turns cloudy/milky
  • Chlorine (Cl₂): Damp litmus paper → Bleaches white
• What is the purpose of flame tests?

  To identify metal ions by flame color
• What are the flame colors for different metal ions?

  • Lithium (Li⁺): Red (Crimson)
  • Sodium (Na⁺): Yellow
  • Potassium (K⁺): Lilac
  • Calcium (Ca²⁺): Orange-red
  • Copper (Cu²⁺): Green-blue
• How do you perform a flame test?

  Clean wire, dip in sample, place in flame
• What happens when metal ions react with sodium hydroxide?

  Some form insoluble hydroxides as precipitates
• What are the precipitates formed by metal ions with NaOH?

  • Aluminium (Al³⁺): White, dissolves in excess NaOH
  • Calcium (Ca²⁺): White, does NOT dissolve
  • Magnesium (Mg²⁺): White, does NOT dissolve
  • Copper (Cu²⁺): Blue
  • Iron(II) (Fe²⁺): Green
  • Iron(III) (Fe³⁺): Brown
• What are the tests for negative ions (anions) and their positive results?

  • Carbonates (CO₃²⁻): Fizzing with dilute acid, confirm with limewater
  • Sulfates (SO₄²⁻): White precipitate with barium chloride
  • Halides (Cl⁻, Br⁻, I⁻): Precipitate with silver nitrate
• What is the advantage of modern instrumental methods in chemical analysis?

  They provide more accurate and faster analysis
• What are some advanced analysis techniques?

  • Flame Emission Spectroscopy: Identifies metal ions using light emission
  • Mass Spectrometry: Identifies molecular mass of compounds
  • Gas Chromatography (GC): Separates and identifies compounds in mixtures
• What are the key points in chemical analysis?

  • Pure substances: Fixed melting & boiling point
  • Formulations: Mixtures for specific purposes
  • Chromatography: Separates based on solubility & movement
  • Gas tests: Specific reactions for gases
  • Flame tests: Identify metal ions by flame color
  • Precipitation tests: Identify metal hydroxides & anions
  • Advanced analysis: Spectroscopy & chromatography for accuracy