Group 7

• Trend in boiling point down group 7

  Increase as relative masses increase leading to stronger vanderwaals forces
• Trend in reactivity down group 7

  Decrease as atoms with a smaller radius attract electrons better
• Trend in oxidising ability down group 7

  Decrease
• A halogen will displace a halide from solution if the halide is lower in the periodic table
• Which halides will be displaced by chlorine

  • Bromide; Orange solution of Br2 made
  • Iodide; Brown solution I2 made
• Which halides get displaced by bromine

  • Iodide; Brown solution of I2 made
• Which halides get displaced by iodide

  None
• Bleach disproportionation reaction


  2NaOH + Cl2 -> NaClO + NaCl + H2O
• Why is making bleach a disproportionation reaction

  Chlorine has been both oxidised and reduced
• Uses of bleach

  • Treating water
  • Bleaching paper and fabrics
  • Cleaning agents
• Water sterlisation disproportionation reaction

  H2O + Cl2 -> 2H+ + Cl- + ClO-
• Water sterilisation in sunlight reaction

  2H2O + Cl2 -> 4H+ + 2Cl- + O2
• Advantages of chlorinating drinking water

  • Destroys microorganisms that cause disease
• Disadvantages of chlorinating water

  • Chlorine can react to make chloroalkanes which are linked to causing cancer
• Trend down group 7 in halide ion reducing power

  Increases down group 7 as ionic radius increases and more shielding occurs so the electrostatic attraction becomes weaker and the outer electron is lost more readily
• Which sulfur containing products can be made when reacting sulfuric acid with halide ions

  • NaHSO4
  • SO2
  • S
  • H2S
• First reaction of sodium halide with sulfuric acid (M = halide)

  • NaM + H2SO4 -> NaHSO4 + HM
• Second reaction for sodium halide with sulfuric acid and which halide doesnt perform this (M = Halide)

  • Chloride doesn't perform this reaction
  • H2SO4 + 2H+ + 2M- -> M2 + SO2 + 2H2O
• Third reaction of sodium halide with sulfuric acid and which halides cant perform this reaction

  • Chloride and Bromide cant perform this reaction
  • H2SO4 + 6H+ + 6I- -> 3I2 + S + 4H2O
• Final reaction of sodium halide with sulfuric acid and which halides cant perform this reaction


  • Chloride and Bromide cannot perform this reaction
  • H2SO4 + 8H+ + 8I- -> 4I2 + H2S + 4H2O
• What would you observe if HCl was produced in a reaction

  White misty fumes
• What would you observe if bromine was made in a reaction

  Orange vapour of Br2
• What would you observe if sulfur was made in a reaction

  Yellow solid
• How would you know if H2S had been produced in a reaction

  rotten egg smell
• Chloride ions with silver nitrate observation and reaction

  • White precipitate formed
  • Ag+ + Cl- -> AgCl
• Bromide ions with silver nitrate observation and reaction

  • Cream precipitate formed
  • Ag+ + Br- -> AgBr
• Iodide ions with silver nitrate observation and reaction

  • Yellow precipitate formed
  • Ag+ + I- -> AgI
• Why do we add nitric acid before this reaction

  To react with any anions other than halides which could result in a false positive
• Which precipitates does dilute NH3 dissolve

  AgCl
• Which percipitates does concerntrated NH3 dissolve

  • AgCl
  • AgBr
• Which precipitate is insoluble with concerntrated NH3

  AgI
• Give an equation for the redox reaction between solid sodium bromide and concentrated sulfuric acid.

  Explain using oxidation states why this is a redox reaction


  • NaBr + H2SO4 -> Br2 + SO2 + Na2SO4
  • Br from -1 to 0 oxidation state (Oxidised)
  • S from +6 to +4 oxidation state (Reduced)