Reduction of Potassium Bichromate by zinc at acidic media

The color of the solution changes from yellow to green and blue

Scientific name: Reduction of Potassium Bichromate by atomic hydrogen

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Acidified Dichromate and Zinc

Восстановление бихромата калия атомарным водородом.

Exothermic reaction. Nitric acid, potassium chromate and zinc

by Marc

Safety

Wear eye protection goggles.

Always follow general safety recommendations. Please note that conducting chemistry experiments you must comply with the relevant legal procedures in your country.

Reaction formula

3 Zn + K2Cr2O7 + 14 HCl → 3 ZnCl2 + 2 CrCl3 + 7 H2O + 2 KCl

Zn + 2 HCl → ZnCl2 + 2 H (in situ)

Step-by-step instruction

  1. Pour 10 ml of hydrochloric acid 2M into a test tube.
  2. Dissolve a small amount of potassium dichromate in the same test tube.
  3. Add a few pieces of zinc.
  4. Observe the formation of gas bubbles and the change in color: yellow - green - blue.

Scientific background

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).

Danger:
Coolness:
Difficulty:

Published on 30 April 2015

  • Fire
  • Heating with fire
  • Explosion
  • Poisoned gas
  • Organic
  • Electricity
  • Solution
  • Oxidation reduction
  • Color change
  • Precipitate
  • Gassing
  • Catalyst