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 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 substances
• How do we draw the starting line in chromatography?

  In pencil so it doesn't move with solvent
• What does the RF value represent in chromatography?

  Ratio of distance moved by substance to solvent
• How can RF values be used in analysis?

  To identify substances by comparison
• How do we test for hydrogen gas?

  By holding a burning splint over it
• What happens when oxygen is present in a test?

  It relights a glowing splint
• What indicates the presence of carbon dioxide?

  Turns lime water cloudy when bubbled
• How does chlorine gas affect damp blue litmus paper?

  It bleaches it, turning it 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?

  White precipitate
• What happens to aluminium hydroxide with excess sodium hydroxide?

  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 do sulfate ions produce when mixed with barium chloride?

  White precipitate
• What are instrumental methods used for in chemical analysis?

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

  Identifies wavelengths emitted by metals
• How does flame emission spectroscopy differ from flame tests?

  It provides precise wavelength identification
• What is an emission line spectrum?

  Pattern of wavelengths emitted by substances
• How can emission line spectra be used in analysis?

  To identify metal ions in samples
• What are the key chemical tests for identifying substances?

  • Hydrogen: Squeaky pop with burning splint
  • Oxygen: Relights glowing splint
  • 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 in performing chromatography?

  1. Draw a pencil line on chromatography paper
  2. Place spots of mixture on the line
  3. Add solvent to the bottom of the paper
  4. Allow solvent to rise by capillary action
  5. Measure distances moved by solvent and substances
  6. Calculate RF values for identification