Group 7

• What is the physical state and color of fluorine (F2)?


  Very pale yellow gas
• What is the physical state and color of chlorine (Cl2)?


  Greenish, reactive gas
• What is the physical state and color of bromine (Br2)?


  Red liquid that gives off dense brown/orange poisonous fumes
• What is the physical state and color of iodine (I2)?


  Shiny grey solid that sublimes to purple gas
• What is the trend in melting and boiling points of halogens down the group?


  • Melting and boiling points increase down the group
  • Larger molecules have more electrons
  • Larger van der Waals forces require more energy to break
• What is the trend in electronegativity of halogens down the group?


  • Electronegativity decreases down the group
  • Atomic radii increase due to more shells
  • Nucleus is less able to attract bonding electrons
• What is the definition of electronegativity?


  It is the tendency of an atom in a molecule to attract electrons in a covalent bond.
• What happens in displacement reactions of halide ions by halogens?


  • A stronger oxidizing agent displaces a weaker one
  • Oxidizing strength decreases down the group
  • Chlorine displaces bromide and iodide; bromine displaces iodide
• What color solution indicates the presence of chlorine in a reaction?


  Very pale green solution (often colorless)
• What color solution indicates the presence of bromine in a reaction?


  Yellow solution
• What color solution indicates the presence of iodine in a reaction?


  Brown solution (sometimes black solid present)
• What is the equation for chlorine displacing bromide ions?


  Cl2(aq) + 2Br–(aq) → 2Cl–(aq) + Br2(aq)
• What is the equation for chlorine displacing iodide ions?


  Cl2(aq) + 2I–(aq) → 2Cl–(aq) + I2(aq)
• What is the equation for bromine displacing iodide ions?


  Br2(aq) + 2I–(aq) → 2Br–(aq) + I2(aq)
• What is the procedure for testing halide ions with silver nitrate?


  1. Make the test solution acidic with nitric acid
  2. Add silver nitrate solution dropwise
  3. Observe precipitate formation
  4. Fluorides: no precipitate
  5. Chlorides: white precipitate
  6. Bromides: cream precipitate
  7. Iodides: pale yellow precipitate
• What is the reaction for chlorides with silver nitrate?

  Ag+(aq) + Cl–(aq) → AgCl(s)
• What is the reaction for bromides with silver nitrate?

  Ag+(aq) + Br–(aq) → AgBr(s)
• What is the reaction for iodides with silver nitrate?

  Ag+(aq) + I–(aq) → AgI(s)
• How can silver halide precipitates be differentiated?


  • Silver chloride dissolves in dilute ammonia
  • Silver bromide dissolves in concentrated ammonia
  • Silver iodide does not react with ammonia
• What is the reaction of fluoride ions with concentrated sulfuric acid?


  NaF(s) + H2SO4(l) → NaHSO4(s) + HF(g)
• What is the observation when fluoride reacts with concentrated sulfuric acid?


  White steamy fumes of HF are evolved
• What is the reaction of chloride ions with concentrated sulfuric acid?


  NaCl(s) + H2SO4(l) → NaHSO4(s) + HCl(g)
• What is the observation when chloride reacts with concentrated sulfuric acid?


  White steamy fumes of HCl are evolved
• What happens when bromide ions react with concentrated sulfuric acid?


  They first undergo an acid-base reaction, then reduce sulfur from +6 to +4 in SO2
• What is the overall equation for the reaction of bromide with concentrated sulfuric acid?


  2NaBr + 3H2SO4 → 2NaHSO4 + SO2 + Br2 + 2H2O
• What is the observation when bromide reacts with concentrated sulfuric acid?


  White steamy fumes of HBr and orange fumes of bromine are evolved
• What is the reaction of iodide ions with concentrated sulfuric acid?


  Iodide ions are the strongest reducing agents and can reduce sulfur to various oxidation states
• What is the overall equation for the reaction of iodide with concentrated sulfuric acid?


  2NaI + 6H2SO4 → 3I2 + S + 4H2O + H2S
• What is the observation when iodide reacts with concentrated sulfuric acid?


  White steamy fumes of HI, black solid and purple fumes of iodine, colorless gas SO2, and yellow solid sulfur are evolved
• What is disproportionation in the context of chlorine reactions?


  • A reaction where an element is both oxidized and reduced
  • Example: Cl2(g) + H2O(l) ⇌ HClO(aq) + HCl(aq)
• What happens when chlorine reacts with water in sunlight?


  2Cl2 + 2H2O → 4H+ + 4Cl- + O2
• What is the observation when chlorine reacts with water in sunlight?


  The greenish color of chlorine water fades as O2 is produced
• What is the reaction of chlorine with cold dilute NaOH solution?


  • Cl2(aq) + 2NaOH(aq) → NaCl(aq) + NaClO(aq) + H2O(l)
  • The color of the halogen solution fades to colorless
• How are chlorates and sulfates named in IUPAC convention?


  • Named with relevant oxidation number in Roman numerals
  • Examples:
  • NaClO: sodium chlorate(I)
  • NaClO3: sodium chlorate(V)
  • K2SO4: potassium sulfate(VI)
  • K2SO3: potassium sulfate(IV)