Group 7

• How does fluorine appear at room temperature?

  A pale yellow gas
• How does chlorine appear at room temperature?

  A greenish gas
• How does bromine appear at room temperature?

  A red-brown liquid
• How does iodine appear at room temperature?

  A black solid
• How does the size of atoms change going down Group 7?

  They get bigger as each atom gains a new shell
• Why are the properties of fluorine considered atypical?

  F-F bond is unexpectedly weak due to repulsion
• How does electronegativity change going down Group 7?

  It decreases as the atom size and shielding effect increase, no longer able to attract electrons
• What is electronegativity and what does it depend on?

  It measures an atom's ability to attract electron density
• What factors affect electronegativity?

  Protons, shielding effect, bonding electrons, atom size
• How do melting point (MP) and boiling point (BP) change going down Group 7?

  They increase as larger atoms have more electrons, so increased van Der Waals force
• How does oxidizing ability change going down Group 7?

  It decreases going down the group
• How does reducing power change going down Group 7?

  Reducing power increases as ions get larger, so electrons are more easily lost
• How do sodium halides react with concentrated sulfuric acid?

  Different reactions occur for each sodium halide
• What are the reactions of sodium chloride with concentrated sulfuric acid?

  • Produces steamy fumes of HCl
  • Solid product is sodium hydrogensulfate
  • No redox reaction occurs
• What are the reactions of sodium bromide with concentrated sulfuric acid?

  • Produces steamy fumes of hydrogen bromide
  • Brown fumes of bromine and colorless sulfur dioxide
  • Bromide ions reduce sulfuric acid to sulfur dioxide
• What are the reactions of sodium iodide with concentrated sulfuric acid?

  • Produces steamy fumes of hydrogen iodide
  • Black solid of iodine and bad egg smell of hydrogen sulfide
  • Sulfur is reduced from +6 to -2
• Why do we see yellow solid sulfur in the reaction between sodium iodide and concentrated sulfuric acid?

  Because sulfur passes through oxidation state 0
• How do metal halides react with silver ions?

  • All react except metal fluoride
  • Silver chloride forms a white precipitate
  • Silver bromide forms a cream precipitate
  • Silver iodide forms a pale yellow precipitate
• What is the equation for the reaction of chlorine with water?

  Cl2 + H2O --> HOCl + HCl
• What is the equation for the reaction between chlorine and aqueous sodium hydroxide?

  Cl2(g) + 2NaOH(aq) --> NaClO(aq) + NaCl(aq) + H2O(l)
• What is the equation for the reaction of sodium chloride with concentrated sulfuric acid?

  NaCl (s) + H2SO4 (l) --> NaHSO4 (aq) + HCl (g)
• Is the reaction between sodium chloride and sulfuric acid a redox reaction?

  No as there is no change in oxidation state, the chloride is too weak a reducing agent.
• Give the two equations for the reaction between sodium bromide and sulfuric acid.

  • NaBr(s) + H2SO4 (l) --> NaHSO4 (aq) + HBr (g)
  • 2H+ + 2Br- + H2SO4 --> SO2 (g) + 2H2O (l) Br2 (g)
• What would we see in the reaction of bromine with sulfuric acid?

  • Steamy fumes of hydrogen bromide
  • Brown fumes of bromine
  • Sulfur dioxide
• What type of reaction is the reaction between sodium chloride and concentrated sulfuric acid?

  Acid-base
• What do we see in the reaction between sodium iodide and concentrated sulfuric acid?

  • Steamy fumes of hydrogen iodide
  • Black solid of iodine
  • Bad egg smell of hydrogen sulfide gas
  • Yellow solid sulfur
  • Colourless sulfur dioxide gas
• What are the two equations for the reaction between sodium iodide and sulfuric acid?

  • NaI (s) + H2SO4 --> NaHSO4 (s) + HI
  • 2H+ + 2I- + H2SO4 --> SO2 + 2H2O + I2
  • 8H+ + 8I- + H2SO4 --> H2S(g) + 4H2O (l) + 4I2 (s)
• What colour solution is formed from this reaction?

  NaI (aq) + Br2 (aq)

  Dark brown, iodine is displaced
• What are the major products formed when chlorine reacts with cold, dilute aqueous sodium hydroxide?

  NaCl and NaClO
• What is the best oxidising agent of F2, F-, I2 and I-?


  F2
• Give a half equation to show the reduction of conc sulfuric acid to hydrogen sulfide with sodium iodide.

  H2SO4 + 8H+ 8e- --> H2S + 4H2O
• Give the overall equation for the reaction of solid sodium iodide with concentrated sulfuric acid.


  8H+ + 8I- + H2SO4 --> H2S + 4I2 + 4H2O
• What is a disproportionation reaction?

  Where a component is both oxidised and reduced
• Give the equation for the formation of sulfur dioxide in the reaction between solid sodium iodide and conc. sulfuric acid.

  2H+ + 2I- + H2SO4 --> SO2 + 2H2O + I2
• What is observed when silver nitrate solution is added to sodium fluoride solution?

  Colourless solution
• What is observed when solid sodium chloride reacts with concentrated sulfuric acid?

  Steamy white fumes of HCl gas
• Give the overall equation for the reaction between solid sodium bromide and conc sulfuric acid.

  2NaBr + 2H2SO4 --> Na2SO4 + Br2 + SO2 + 2H2O
• Reaction of chlorine with water in bright light

  2Cl2 + 2H2O --> 4HCl + O2
• Reversible Dissolving of NaClO and water

  NaClO + H2O --> Na+ + OH- + HOCl
• Reaction of Chlorine to produce NaClO

  Cl2 + 2NaOH —> NaClO + NaCl + H2O