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Chromate Formula

Last updated date: 25th Feb 2024
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Chromate Ion Formula

The chromate formula is one of the most commonly used formulas in chemistry. The chromate ion is one of the numerous polyatomic ions that are frequently used in the creation of insoluble salts. Chromate is a chromium oxoanion and a divalent inorganic anion generated by removing two protons from chromic acid, according to the definition. It is frequently a conjugate base of hydrogen chromate and works as a powerful oxidising agent.

The chromate anion, CrO42-, is found in chromate salts. The dichromate anion, Cr2O72-, is found in dichromate salts. They are relatively strong oxidising agents that are chromium oxyanions in the 6+ oxidation state. The chromate and dichromate ions can interconvert in an aqueous solution.

This page will study chromate formula, chromate ion and chromate ion formula in detail.

Structure of Chromate Ion Formula 

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Chemical Properties of Chromate

Chromates react with hydrogen peroxide to produce compounds in which one or more oxygen atoms are replaced by peroxide. CrO(O2)2, an uncharged covalent molecule that may be extracted into ether, is produced in acid solution as the unstable blue peroxo complex Chromium(VI) oxide peroxide, CrO(O2)2. When pyridine is added, the complex CrO(O2)2py is formed, which is more stable.

Physical Properties of Chromate




Yellow powder




Generally insoluble in water.

Chromate Ion

In acid solution, the chromate ion is a powerful oxidising agent. Chromium(III) hydroxide is formed when the chromate ion reacts with water in an alkaline solution.

CrO42-+ 4 H2O + 3 e− → Cr(OH)3 + 5 OH−

When potassium chromate interacts with barium nitrate, barium chromate and potassium nitrate are formed.

K2CrO4 + Ba(NO3)2 ↔ BaCrO4 + 2KNO3

Applications of Chromate Ion

  1. The sodium and potassium salts of chromate are extremely corrosive and are used in enamels, leather finishing, and metal rustproofing.

  2. Potassium chromate crystals are used as a pigment in dyes and inks. It is poisonous if eaten.

  3. Wax is used to make children's crayons, which is mainly paraffin and is non-toxic. Lead chromate is used in industrial crayons, which is not safe.

  4. In chrome plating, it's used to keep the metal from corroding.

  5. In 1985, over 136,000 tonnes (150,000 tonnes) of hexavalent chromium, primarily sodium dichromate, were produced. Chrome plating uses chromates and dichromates to protect metals from corrosion while also improving paint adhesion. Heavy metal chromate and dichromate salts, lanthanides, and alkaline earth metals are employed as pigments because they are only very little soluble in water. Chrome yellow, a lead-containing pigment, was used for a long time before environmental rules made it illegal. Chromates and dichromates, when used as oxidising agents or titrants in a redox chemical reaction, change to trivalent chromium, Cr3+, whose salts often have a characteristic colour.

Minerals of Chromate

Minerals containing chromium are uncommon. Crocoite, PbCrO4, is the most common chromate mineral, occurring as magnificent long red crystals. The Atacama Desert contains rare potassium chromate minerals and related chemicals. Lópezite, the only known dichromate mineral, is one of them.


The chromate ion is one of many polyatomic ions commonly employed in the production of insoluble salts. According to the definition, chromate is a chromium oxoanion and a divalent inorganic anion formed by removing two protons from chromic acid. It is frequently a hydrogen chromate conjugate base and is a powerful oxidising agent. In dyes and inks, potassium chromate crystals are employed as a pigment. If consumed, it is poisonous.

FAQs on Chromate Formula

Q1. Is There a Distinction Between Dichromate and Chromate?

Ans. The main distinction between chromate and dichromate is that chromate appears bright yellow, whereas dichromate appears brilliant orange. Anions containing chromium and oxygen atoms are known as chromate and dichromate. As a result, they are chromium oxyanions.

Q2. Is Chromate a Metal or a Non-Metal?

Ans. One chromium atom (in its +6 oxidation state) and four oxide atoms make up the ion chromate. In a basic environment, they can be produced by reacting chromium(III) oxide with a metal oxide. Reactions with reducing agents can destroy them.

Q3. Why Does Potassium Chromate Have a Yellow Colour?

Ans. In an aqueous solution, the yellow chromate ion and the orange dichromate ion are in equilibrium. The orange colour of the potassium chromate solution changes to yellow when sodium hydroxide is introduced. Hydrogen ions are removed from the solution when sodium hydroxide combines with them.