The color of the solution changes from yellow to green and blue
name: Reduction of Potassium Bichromate by atomic hydrogen
Acidified Dichromate and Zinc
Восстановление бихромата калия атомарным водородом.
Exothermic reaction. Nitric acid, potassium chromate and zinc
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3 Zn + K2Cr2O7 + 14 HCl → 3 ZnCl2 + 2 CrCl3 + 7 H2O + 2 KCl
Zn + 2 HCl → ZnCl2 + 2 H (in situ)
- Pour 10 ml of hydrochloric acid 2M into a test tube.
- Dissolve a small amount of potassium dichromate in the same test tube.
- Add a few pieces of zinc.
- Observe the formation of gas bubbles and the change in color: yellow - green - blue.
The interaction of zinc with acid generated atomic hydrogen which has not yet bonded into a molecule. Atomic hydrogen is a very strong reducing agent and recovers Cr(VI) to Cr(III) and Cr(II).