The reaction of halide salts with concentrated sulfuric acid

• Explanation of differing reducing power of halides

  A reducing agent donates electrons.

  The reducing power of the halides increases down group 7

  They have a greater tendency to donate electrons.

  This is because as the ions get bigger it is easier for the

  outer electrons to be given away as the pull from the nucleus

  on them becomes smaller.
• Fluoride and Chloride with concentrated sulfuric acid

  F- and Cl- ions are not strong enough reducing agents to reduce the S in H2SO4.

  No redox reactions occur. Only acid-base reactions occur
• Fluoride and Chloride with concentrated sulfuric acid Equations

  NaF(s) + H2SO4(l) -> NaHSO4(s) + HF(g)

  Observations: White steamy fumes of HF are evolved.

  NaCl(s) + H2SO4(l) -> NaHSO4(s) + HCl(g)

  Observations: White steamy fumes of HCl are evolved.
• What observations are seen in the reaction of bromide with sulfuric acid?

  • White steamy fumes of HBr
  • Orange fumes of bromine (Br₂)
  • Colourless, acidic gas SO₂
• What is the reduction product in the reaction of bromide with sulfuric acid?

  Sulfur dioxide (SO₂)
• What observations are seen in the reaction of iodide with sulfuric acid?

  • White steamy fumes of HI
  • Black solid and purple fumes of iodine (I₂)
  • Colourless, acidic gas SO₂
  • Yellow solid of sulfur
  • H₂S (hydrogen sulfide), a gas with a bad egg smell
• What is an acid - base reaction

  An acid-base reaction is a chemical reaction where an acid donates a proton (H⁺) to a base.

  General equation:

  Acid+Base→Salt+Water