AQA AS Level Chemistry Group 7 Summary

Group 7
Observations at Room Temperature Fluorine
• NaF + H2SO 4 à NaHSO4 + HF
• Fluorine = Pale Yellow Gas
o White misty fumes of HF
• Chlorine = Green Gas
• Bromine = Orange-Brown Liquid
• Iodine = Grey Solid
Chlorine
• NaCl + H2SO 4 à NaHSO4 + HCl
o White misty HCl fumes
Trends Down the Group • Cl2 + NaOH à NaClO + NaCl + H2O
• Electronegativity Decreases o NaOH must be cold and dilute
• Melting Point / Boiling Point Increases o NaClO is bleach, used to bleach paper/textiles and to treat water
• Oxidising Power Decreases
• Reducing Power Increases • Cl2 + H 2O ⇌ HClO + HCl
o Chlorate (I) ions kill bacteria
o Chlorine is used in drinking water and swimming pools

• Chlorine is toxic and harmful if breathed in
• The benefits of using chlorine outweigh the health risks
Halogen Displacement Reactions
• Chlorine decomposes water in sunlight:
• Chlorine = Very Pale Green / Colourless Solution
• 2Cl2 + 2H 2O à 4H+ + 4Cl- + O2
• Bromine = Yellow Solution
• Iodine = Brown Solution
• Chlorine can displace bromide and iodide ions
• Bromine can displace iodide ions
Iodine
• NaI + H 2SO 4 à NaHSO4 + HI
o White misty fumes of HI
Bromine • 2HI + H2SO4 à I2 + SO2 + 2H2O
o Colourless SO2 gas
• NaBr + H2SO4 à NaHSO4 + HBr o Purple I2 vapour or Black I2 Solid
o Misty white fumes of HBr • 6HI + SO2 à H2S + 3I2 + 2H 2O
• 2HBr + H2SO 4 à Br2 + SO2 + 2H2O o Bad smells of H 2S
o Colourless SO2 gas • 4HI + SO2 à S + 2I2 + 2H2O
o Orange Br2 fumes o Yellow S solid