Wednesday, 20 June 2018

Uses of potassium dichromate

Uses of potassium dichromate

i) Used as oxidizing agent.
ii) Used in making other chromium compounds.
iii) Used in detection of chloride ion in chromyl chloride test.
iv) Used in tanning of leather.
v) Used in determination of ferrous ammonium sulphate (Mohr’s salt) & iodine in volumetric analysis.
vi) Used in dyeing.

Properties of potassium dichromate 6

Action on sulphur dioxide, on primary & secondary alcohols & formation of chromyl chloride

primary & secondary alcohols & formation of chromyl chloride 


Properties of potassium dichromate 5

Action on hydrogen sulphide

         When hydrogen sulphide is passed through acidified K2Cr2O7 solution. Hydrogen sulphide gas is oxidized to sulphur (pale yellow precipitate) & potassium dichromate is reduced to chromic sulphate (green).
Hydrogen sulphide oxidized into pale yello sulphur

Properties of potassium dichromate 4

iii) Action on potassium iodide

       Acidified potassium dichromate oxidizes potassium iodide into iodine (brown colour).

potassium iodide oxidizes into iodine

Properties of potassium dichromate 3

ii) Action on ferrous sulphate

 Acidified potassium dichromate (orange red solution) oxidizes ferrous sulphate to ferric sulphate (green colour).

Properties of Potassium dichromate 2

2) Oxidizing properties

         Potassium dichromate is a powerful oxidizing agent in acidic medium due to +6 oxidation state of chromium (in potassium dichromate) which changes to +3 (in chromium sulphate).

i) In acidic medium, it acts as oxidizing agent because of gain of electrons Cr
reduced to Cr³.

Properties of potassium dichromate

Properties of potassium dichromate (K2Cr2O7)

Potassium dichromate is orange red crystal & water soluble.

1) Action of Alkali/base (KOH): 
      When potassium dichromate reacts with potassium hydroxide (KOH) then yellow coloured solution of potassium chromate is formed.