6 NH4I + (NH4)2Cr2O7 + 7 H2SO4 3 I2 + Cr2(SO4)3 + 4 (NH4)2SO4 + 7 H2O

This is an oxidation-reduction (redox) reaction:

6 I-I - 6 e- 6 I0 (oxidation)

2 CrVI + 6 e- 2 CrIII (reduction)

NH4I is a reducing agent, (NH4)2Cr2O7 is an oxidizing agent.

Reactants:

  • NH4I
    • (NH4)2Cr2O7Ammonium dichromate source: wikipedia, accessed on: 2019-09-27source: wikidata, accessed on: 2019-09-02source: ICSC, accessed on: 2019-09-04
      • Other names: Ammonium bichromate source: wikipedia, accessed on: 2019-09-27source: ICSC, accessed on: 2019-09-04, Ammonium pyrochromate source: wikipedia, accessed on: 2019-09-27, Diammonium dichromate (VI) source: ICSC, accessed on: 2019-09-04, Dichromic acid, diammonium salt source: ICSC, accessed on: 2019-09-04
      • Appearance: Orange-red crystals source: wikipedia, accessed on: 2019-09-27; Orange-to-red crystals source: ICSC, accessed on: 2019-09-04
    • H2SO4Sulfuric acid source: wikipedia, accessed on: 2019-09-27source: wikidata, accessed on: 2019-09-07source: NIOSH NPG, accessed on: 2019-09-02
      • Other names: Oil of vitriol source: wikipedia, accessed on: 2019-09-27source: wikidata, accessed on: 2019-09-07source: ICSC, accessed on: 2019-09-04source: NIOSH NPG, accessed on: 2019-09-02, Sulfuric acid, concentrated (> 51% and < 100%) source: ICSC, accessed on: 2019-09-04, H2SO4 source: wikidata, accessed on: 2019-09-07
      • Appearance: Clear, colorless liquid source: wikipedia, accessed on: 2019-09-27; Odourless colourless oily hygroscopic liquid source: ICSC, accessed on: 2019-09-04; Colorless to dark-brown, oily, odorless liquid. [Note: Pure compound is a solid below 51°F. Often used in an aqueous solution.] source: NIOSH NPG, accessed on: 2019-09-02

    Products:

    • I2
      • Names: Iodine source: ICSC, accessed on: 2019-09-04source: NIOSH NPG, accessed on: 2019-09-02, Jod source: ICSC, accessed on: 2019-09-04, Iode source: ICSC, accessed on: 2019-09-04
      • Appearance: Bluish black or dark purple crystals with pungent odour source: ICSC, accessed on: 2019-09-04; Violet solid with a sharp, characteristic odor. source: NIOSH NPG, accessed on: 2019-09-02
    • Cr2(SO4)3Chromium(III) sulfate source: wikipedia, accessed on: 2019-09-27source: wikidata, accessed on: 2019-09-02
      • Other names: Basic chromium sulfate source: wikipedia, accessed on: 2019-09-27, Chromic sulfate source: wikipedia, accessed on: 2019-09-27
      • Appearance: Reddish-brown crystals (anhydrous), purple crystals (hydrated) source: wikipedia, accessed on: 2019-09-27
    • (NH4)2SO4Ammonium tetraoxosulfate (VI) source: wikipedia, accessed on: 2019-09-27
      • Other names: Ammonium sulphate source: wikipedia, accessed on: 2019-09-27source: wikidata, accessed on: 2019-09-02, Ammonium sulfate source: wikipedia, accessed on: 2019-09-27source: wikidata, accessed on: 2019-09-02, Ammonium sulfate (2:1) source: wikipedia, accessed on: 2019-09-27source: wikidata, accessed on: 2019-09-02
      • Appearance: Fine white hygroscopic granules or crystals. source: wikipedia, accessed on: 2019-09-27
    • H2OWater, oxidane source: wikipedia, accessed on: 2019-09-27
      • Other names: Water (H2O) source: wikipedia, accessed on: 2019-09-27, Hydrogen hydroxide (HH or HOH) source: wikipedia, accessed on: 2019-09-27, Hydrogen oxide source: wikipedia, accessed on: 2019-09-27
      • Appearance: White crystalline solid, almost colorless liquid with a hint of blue, colorless gas source: wikipedia, accessed on: 2019-09-27