C8 - Chemical Analysis

• What defines a pure substance?

  A single element or compound
• What is a formulation?

  A mixture designed as useful product
• Why are alloys used instead of pure metals?

  They are harder than pure metals
• Describe the process of paper chromatography.

  1. Draw a start line, spot mixture on it.
  2. Add small amount of solvent to beaker
  3. Hang paper on rod and place in beaker.
  4. Solvent travels up, separating components.
  5. Remove paper before solvent reaches end, mark finish, dry.
  6. Separation due to different affinities.
  7. Paper is stationary phase, solvent is mobile phase.
• How is the Rf value calculated in chromatography?

  Distance spot moved / distance solvent moved
• What does an Rf value of 0.85 indicate about a compound's affinity in paper chromatography?

  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 precipitates are formed in the sodium hydroxide test for metal 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 observation in the test for carbonate anions?

  Fizzing is observed
• What happens when dilute acid is added to carbonate anions?

  CO2 is released
• What type of precipitate forms in the test for sulfate anions?

  White precipitate
• What reagent is used to test for sulfate anions?

  Solution containing $Ba^{2+}$ cations
• What observation indicates the presence of sulfate anions when barium chloride is added?

  White precipitate of $BaSO_4$ forms
• What type of test is the reaction with sulfates to form a white precipitate?

  Test for barium (II)
• What reagent is used in the test for halide anions?

  Solution of $AgNO_3$
• What precipitate indicates the presence of chloride anions?

  White precipitate, silver chloride
• What precipitate indicates the presence of bromide anions?

  Cream precipitate, silver bromide
• What precipitate indicates the presence of iodide anions?

  Yellow precipitate, silver iodide
• What are instrumental methods known for?

  Accurate, sensitive, and rapid methods
• When are instrumental methods particularly useful?

  When sample amount is small
• Describe the key aspects of flame emission spectroscopy.

  1. Used for identifying/quantifying metal ions.
  2. Spectroscope measures emitted light's wavelength.
  3. Provides definite identification of metal.
  4. Concentration from intensity of light emitted.
  5. Concentration vs intensity graph helps determine concentration.
• What are cations and anions?

  Positive and negative ions
• What is the product of the reaction between copper(II) ions and hydroxide ions?

  $Cu(OH)_2(s)$
• What is the product of the reaction between iron(II) ions and hydroxide ions?

  $Fe(OH)_2(s)$
• What is the product of the reaction between iron(III) ions and hydroxide ions?

  $Fe(OH)_3(s)$
• What is the product of the reaction between calcium ions and hydroxide ions?

  $Ca(OH)_2(s)$
• What is the product of the reaction between magnesium ions and hydroxide ions?

  $Mg(OH)_2(s)$
• What is the product of the reaction between aluminium ions and hydroxide ions?

  $Al(OH)_3(s)$