Chemical Analysis

• What is the importance of obtaining pure substances in chemistry?

  It is crucial for 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 purpose.
• How is chromatography used in chemical analysis?

  To separate substances in a mixture.
• What is the stationary phase in chromatography?

  It is the medium substances move up on.
• What is the mobile phase in chromatography?

  It is the solvent that moves up the paper.
• Why do we draw the starting line in pencil in chromatography?

  To prevent it from moving with the solvent.
• How do we calculate the RF value in chromatography?

  By comparing the distance moved by the substance to the solvent.
• What does RF stand for in chromatography?

  Retention factor.
• How can RF values help in identifying substances?

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

  By holding a burning splint over the test tube.
• What sound indicates the presence of hydrogen gas?

  A squeaky pop sound.
• What happens to a glowing splint in the presence of oxygen?

  It relights.
• What does carbon dioxide do to lime water?

  Turns it cloudy when bubbled through.
• What effect does chlorine gas have on damp blue litmus paper?

  It bleaches it white.
• How can we test for metals using flame tests?

  By observing the color of the flame produced.
• What color flame does lithium produce?

  A crimson flame.
• What color flame does sodium produce?

  A yellow flame.
• What color flame does potassium produce?

  A lilac flame.
• What color flame does calcium produce?

  An orange-red flame.
• What color flame does copper produce?

  A 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.
• What color precipitate do copper(II) ions form with sodium hydroxide?

  A blue precipitate.
• What color precipitate do iron(II) ions form with sodium hydroxide?

  A green precipitate.
• What color precipitate do iron(III) ions form with sodium hydroxide?

  A 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?

  A white precipitate of silver chloride.
• What precipitate is formed when bromide ions are present?

  A cream precipitate of silver bromide.
• What precipitate is formed when iodide ions are present?

  A yellow precipitate of silver iodide.
• What do sulfate ions produce when mixed with barium chloride?

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

  To accurately determine substances present.
• How does flame emission spectroscopy work?

  It analyzes light emitted by a flame.
• What is the advantage of using flame emission spectroscopy over traditional flame tests?

  It provides accurate identification of metal ions.
• What is an emission line spectrum?

  A spectrum showing wavelengths emitted by substances.
• How can emission line spectra be used in chemical analysis?

  To identify metal ions based on emitted wavelengths.
• 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
  • Metals: Flame tests and sodium hydroxide reactions
  • Halides: Silver nitrate test
  • Sulfates: Barium chloride test
• What are the differences between traditional tests and instrumental methods in chemical analysis?

  Traditional tests:

  • Simple and cost-effective
  • Slower and less accurate

  
  

  Instrumental methods:

  • Accurate, sensitive, and fast
  • Require expensive equipment