Topic 8- chemical analysis

• What is a pure substance?


  A single element or compound
• How is a formulation created?


  It is a mixture of compounds in measured quantities
• Why are alloys used instead of pure metals?


  Alloys are harder than pure metals
• What is the process of paper chromatography?


  1. Draw a start line on paper
  2. Spot mixture on the line
  3. Fill a beaker with solvent
  4. Hang paper in the beaker
  5. Solvent travels up, separating components
  6. Mark finish line before solvent reaches end
  7. Paper is the stationary phase; solvent is mobile
• What is the purpose of the start line in paper chromatography?

  To spot the mixture for separation
• How is Rf calculated in chromatography?

  Distance moved by the spot / distance moved by solvent
• What does an Rf value of 0.85 indicate about a compound?

  It has a higher affinity for the solvent
• What are the tests for hydrogen, oxygen, carbon dioxide, and chlorine?

  • Hydrogen: pop with burning splint
  • Oxygen: glowing splint relights
  • Carbon dioxide: turns limewater milky
  • Chlorine: bleaches damp litmus paper
• What are the flame test results for different metal compounds?


  • Lithium: crimson red flame
  • Sodium: yellow flame
  • Potassium: lilac flame
  • Calcium: orange red flame
  • Copper: green flame
• What do the sodium hydroxide test results indicate for different ions?


  • Copper(II): blue precipitate
  • Iron(II): dirty green precipitate
  • Iron(III): brown precipitate
  • Al3+, Ca2+, Mg2+: white precipitates; Al(OH)3 dissolves in excess NaOH
• What is the reaction for copper(II) with sodium hydroxide?


  Cu$^{2+}$(aq) + 2OH$^{-}$(aq) → Cu(OH)$_{2}$(s)
• What is the reaction for iron(II) with sodium hydroxide?


  Fe$^{2+}$(aq) + 2OH$^{-}$(aq) → Fe(OH)$_{2}$(s)
• What is the reaction for iron(III) with sodium hydroxide?


  Fe$^{3+}$(aq) + 3OH$^{-}$(aq) → Fe(OH)$_{3}$(s)
• How do you test for carbonate anions?


  Add dilute acid and observe fizzing
• What is the reaction for sodium carbonate with hydrochloric acid?


  Na$_{2}$CO$_{3}$ + 2 HCl → 2 NaCl + H$_{2}$O + CO$_{2}$
• How do you test for sulfate ions?


  Add Ba$^{2+}$ solution and observe white precipitate
• What is the reaction for potassium sulfate with barium chloride?


  K$_{2}$SO$_{4}$ + BaCl$_{2}$ → 2 KCl + BaSO$_{4}$
• What do silver nitrate tests indicate for halides?


  Chlorides form white, bromides cream, iodides yellow precipitate
• What is the reaction for chloride ions with silver nitrate?


  Ag$^{+}$ + Cl$^{-}$ → AgCl
• What is the reaction for bromide ions with silver nitrate?


  Ag$^{+}$ + Br$^{-}$ → AgBr
• What is the reaction for iodide ions with silver nitrate?


  Ag$^{+}$ + I$^{-}$ → AgI
• What are instrumental methods in chemistry?


  Accurate, sensitive, and rapid methods
• What is flame emission spectroscopy?


  • Identifies metal ions in solution
  • Measures concentration of metal ions
  • Spectroscope measures emitted light wavelength
  • Allows for definite identification
  • Intensity of light indicates concentration
• What are cations and anions?

  Cations are positive ions; anions are negative ions