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ChemWiki: The Dynamic Chemistry E-textbook > Development Details > Approaches > Demos > Additional Demos > The Chemistry of the Halogens

The Chemistry of the Halogens

Chemical Concepts Demonstrated

  • Oxidation/reduction chemistry of halogens and their halides
  • Relative strengths of oxidizing and reducing agents

Demonstration

Prepare three solutions each of NaI (aq), NaBr (aq), and NaI (aq).

  1. Cl2(aq) is added to one of the NaI(aq) solutions and Br2(aq) to another. CH2Cl2 is added to each of the test tubes.  The tubes are stoppered and shaken.
  2. Cl2(aq) is added to one of the NaBr(aq) solutions and I2(aq) to another. CH2Clis added to each of the test tubes.  The tubes are stoppered and shaken.
  3. Br2(aq) is added to one of the NaCl(aq) solutions and I2(aq) to another. CH2Clis added to each of the test tubes.  The tubes are stoppered and shaken.
  4. 0.1M Fe3+ is added to each of the remaining halide solutions. CH2Clis added to each of these test tubes.  The tubes are stoppered and shaken.

Observations

The halogen has been extracted into the bottom organic phase.

    1. The metallic color of iodine can be seen in both tubes in the first set of reactions. 
    2. The reddish color of bromine can be seen in the first test tube but not in the second.
    3. The yellow color of chlorine can NOT be seen in either of the test tubes.
    4. Only iodine has been extracted from the halide solutions reacted with Fe3+.

Explanations (including important chemical equations)

1. Cl2(aq) + 2 NaI(aq) → 2 NaCl (aq) + I2(aq) 

    Br2(aq) + 2 NaI(aq) → 2 NaBr(aq) + I2(aq)

2. Cl2(aq) + 2 NaBr(aq) → 2 NaCl (aq) + Br2(aq)

    I2(aq) + 2 NaBr(aq) → 2 NaI(aq) + Br2(aq)

3. Br2(aq) + 2 NaCl(aq) → 2 NaBr(aq) + Cl2(aq)

    I2(aq) + 2 NaCl(aq) → 2 NaI(aq) + Cl2(aq)

4. Fe3+ (aq) +  NaI (aq) ---> Fe2+ (aq) + I2(aq)

X2 (aq) + 2 Y (aq) 2 X (aq) + Y2 (aq)

  • X2 must be a stronger oxidizing agent than Y2, and Y must be a stronger reducing agent than X in order for the reactions to occur.
  • Cl2 is a stronger oxidizing agent than Br2. Br2 is a stronger oxidizing agent than I2. ( Cl2 > Br2> I2)
  • I- is a better reducing agent than Br -.  Br - is a better reducing agent than Cl-. (I-> Br -> Cl-)
  • Fe3+ is a stronger oxidizing agent than I2, but not as strong as Br2. ( Cl2 > Br2> Fe3+ >I2)

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Last Modified
10:30, 2 Oct 2013

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