Question

The color of ${{K}_{2}}C{{r}_{2}}{{O}_{7}}$ changes from red orange to lemon yellow on treatment with aqueous KOH because of:

Answer 1

${{K}_{2}}C{{r}_{2}}{{O}_{7}}$ is an inorganic compound whose name is potassium dichromate and it is treated with aqueous KOH means it is being treated in an alkaline solution. The dichromate ion is converted into chromate ion in the alkali solution.

Complete answer:
Potassium dichromate whose formula is ${{K}_{2}}C{{r}_{2}}{{O}_{7}}$, is a popular inorganic chemical reagent used as an oxidizing agent in a variety of laboratory and industrial settings. It is acutely and chronically toxic to health, as are all hexavalent chromium compounds. It has a vivid red-orange hue and is a crystalline ionic solid.
When the potassium dichromate is treated with aqueous KOH then there will be the formation of potassium chromate as aqueous KOH is an alkaline medium. The formula of potassium chromate is ${{K}_{2}}Cr{{O}_{4}}$. The inorganic compound potassium chromate has the formula ${{K}_{2}}Cr{{O}_{4}}$. The potassium salt of chromate anion is this yellow solid. It's a common chemical used in laboratories.
So, first, the color of potassium dichromate is red-orange, and due to the formation of potassium chromate the color changes to lemon yellow. The reaction is given below:
${{K}_{2}}C{{r}_{2}}{{O}_{7}}+2KOH\to 2{{K}_{2}}Cr{{O}_{4}}+{{H}_{2}}O$
Both potassium chromate and potassium dichromate are strong oxidizing agents and it is used in many organic reactions.

Note:
The potassium dichromate is a strong oxidizing agent which can be used on many organic compounds like alcohols, aldehydes, etc to convert them directly to carboxylic acids. It is also used in titrations and the manufacture of dyes.