REACTIONS OF SODIUM HALIDES + CONC H2SO4

• WHAT REACTION DEMONSTRATES REDUCING POWERS OF HALIDE IONS?

  solid sodium halides reacting with concentration sulfuric acid
• REACTION OF SODIUM CHLORIDE WITH CONCENTRATED SULFURIC ACID?

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

  -> acid-base reaction

  -> not redox (Cl- too weak a reducing agent to reduce sulfur)

  -> HCl (g) = steamy fumes
• REACTION OF SODIUM BROMIDE WITH CONCENTRATED SULFURIC ACID?

  NaBr (s) + H2SO4 (l) -> NaHSO4 (s) + HBr (g)

  -> acid-base reaction

  -> HBr (g) = steamy fumes

  2H+ + 2Br- + H2SO4 (l) -> SO2 (g) + 2H2O (l) + Br2 (l)

  -> redox reaction (exothermic)

  -> Br2 (l) = some vaporises to produce brown fumes

  -> Br- strong enough reducing agent to reduce H2SO4 -> SO2
• REACTION OF SODIUM IODIDE AND CONCENTRATED SULFURIC ACID?

  NaI (s) + H2SO4 (l) -> NaHSO4 (s) + HI (g)

  -> acid-base reaction

  -> HI (g) = steamy fumes

  2H+ + 2I- + H2SO4 (l) -> SO2 (g) + 2H2O (l) + I2 (s)

  -> passes through redox reaction

  8H+ + 8I- + H2SO4 (l) -> H2S (g) + 4H2O (l) + 4I2 (s)

  -> redox reaction

  -> may also see some yellow solid sulfur

  -> H2S (g) = bad egg smell

  -> 4I2 (s) = black solid

  -> I- strong enough reducing agent to reduce H2SO4 -> SO2 -> H2S