Read the passage carefully and answer the questions.

Sodium dichromate $Na_2Cr_2O_7$ and Potassium dichromate $K_2Cr_2O_7$, are strong oxidizing agents; in acidic solution, its oxidising action can be represented as follows:

$Cr_2{O_7}^{2-}+ 14H^++ 6e^-→2Cr^{3+}+ 7H_2O$ $(E° = 1.33V)$

The chromates and dichromates are interconvertible in aqueous solution depending upon pH of the solution. The chromate ion is tetrahedral whereas the dichromate ion consists of two tetrahedra sharing one corner with Cr-O-Cr bond angle of 126°

Potassium permanganate is prepared by fusion of $MnO_2$ with an alkali metal hydroxide and an oxidising agent like $KNO_3$. This produces the dark green $K_2MnO_4$ which disproportionates in a neutral or acidic solution to give permanganate. It is a strong oxidizing agent. Hydrogen ion concentration of the solution plays an important part in the reduction of permanganate to manganate, manganese dioxide and manganese(II) salt.

Potassium permanganate forms dark purple (almost black) crystals which are isostructural with those of $KClO_4$. The salt is not very soluble in water (6.4 g/100 g of water at 293 K), but when heated it decomposes at 513 K.

Potassium dichromate is used in the leather industry because of its nature as

Oxidant

The correct answer is Option (1) → Oxidant

Core Concept

Potassium dichromate (K₂Cr₂O₇) is a strong oxidizing agent, especially in acidic medium. Its industrial uses depend on this oxidizing property.

Option-wise Explanation

1. Oxidant

K₂Cr₂O₇ contains chromium in the +6 oxidation state, which readily gets reduced to Cr³⁺. During this reduction, it oxidizes other substances. In the leather industry, it helps in tanning and treatment processes by oxidizing organic impurities and aiding in preservation. This is the correct reason.

2. Reductant

A reductant donates electrons and itself gets oxidized. Dichromate does the opposite — it gains electrons (gets reduced). Hence it is not a reducing agent.

3. Alkali media

This refers to basic conditions, not a chemical nature. Although chromate–dichromate equilibrium depends on pH, its use in leather processing is not because it provides an alkaline medium.

4. Disproportionating media

Disproportionation means the same element undergoes oxidation and reduction simultaneously. Dichromate mainly acts as an oxidizing agent; it is not used for leather processing due to any disproportionation property.