FormulasChemistry FormulasDichromate Formula 

Dichromate Formula 

Dichromate Formula


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    Dichromate refers to the dichromate ion, which is an inorganic chemical species represented by the formula Cr2O72-. The dichromate ion consists of two chromium atoms (Cr) covalently bonded to seven oxygen atoms (O) in a linear arrangement.

    The dichromate ion is a polyatomic ion with the chemical formula Cr2O72-. It consists of two chromium atoms (Cr) bonded to seven oxygen atoms (O). The dichromate ion is commonly found in various compounds and salts, such as potassium dichromate (K2Cr2O7) and sodium dichromate (Na2Cr2O7).

    Dichromates are known for their bright orange color and their strong oxidizing properties. They are widely used in industrial processes, including metal finishing, tanning, and the production of pigments and dyes. Additionally, dichromates are utilized in analytical chemistry as oxidizing agents and in certain laboratory reactions.

    The formula of Dichromate Formula


    Structure of Dichromate Formula

    The dichromate ion consists of two chromium atoms (Cr) covalently bonded to seven oxygen atoms (O) in a linear arrangement. Each chromium atom is bonded to three oxygen atoms, and one oxygen atom is shared between the two chromium atoms, forming a bridging bond.

    Molecular Mass of Dichromate Formula

    The molecular mass of the dichromate ion can be calculated by summing the atomic masses of its constituent elements:

    – Atomic mass of chromium (Cr) = 51.9961 g/mol

    – Atomic mass of oxygen (O) = 15.9994 g/mol

    Molecular mass of dichromate (Cr2O72-) = (2 * 51.9961) + (7 * 15.9994) = 207.2 g/mol

    Physical Properties of Dichromate Formula

    Color: The dichromate ion is orange-red in color.

    Solubility: Dichromates are generally soluble in water and form colored solutions.

    Melting and Boiling Points: The melting and boiling points of dichromates vary depending on the specific compound and hydration state.

    Chemical Properties of Dichromate Formula

    Oxidizing Agent: Dichromate ions are powerful oxidizing agents and can readily accept electrons, undergoing reduction reactions while oxidizing other substances.

    Acidic Conditions: In acidic solutions, the dichromate ion can be reduced to form the chromate ion (CrO42-).

    Stability: Dichromates are relatively stable under normal conditions but can decompose when exposed to heat or other reducing agents.

    Toxicity: Hexavalent chromium compounds, including dichromates, are toxic and can have harmful effects on human health and the environment.

    Uses of Dichromate Formula

    Pigments: Dichromates have been used as pigments, particularly in the production of orange, yellow, and green paints and dyes.

    Corrosion Inhibitors: Dichromate compounds are utilized as corrosion inhibitors for metals, protecting them from rust and corrosion.

    Chemical Reactions: Dichromates are employed in various chemical reactions, such as in the synthesis of organic compounds and as catalysts.


    In conclusion, the dichromate ion, with the chemical formula Cr2O72-, is composed of two chromium atoms (Cr) bonded to seven oxygen atoms (O). It is found in compounds and salts, and it is characterized by its vibrant orange color. Dichromates are extensively used in industrial applications such as metal finishing, tanning, and the manufacturing of pigments and dyes. They are also valuable in analytical chemistry as oxidizing agents and for specific laboratory reactions. The distinctive properties and versatility of dichromates make them significant compounds in various fields.

    It’s important to note that the use of dichromate compounds, especially hexavalent chromium, is restricted or regulated in many countries due to their toxicity and environmental impact. Safer alternatives are often sought for many applications to minimize the risks associated with dichromates. Proper safety precautions should be followed when handling dichromates to avoid exposure and environmental contamination.

    Solved example on the Dichromate Formula

    Example 1: What is the formula for a compound formed when sodium reacts with dichromate?


    – The sodium cation has a charge of +1, while the dichromate ion has a charge of -2.

    – To balance the charges, we need two sodium ions for every dichromate ion.

    – Therefore, the formula for the compound formed is Na2Cr2O7.

    Example 2: How many oxygen atoms are present in one dichromate ion?


    – The formula for the dichromate ion is Cr2O72-.

    – In one dichromate ion, there are seven oxygen atoms (O).

    – Therefore, there are a total of seven oxygen atoms in one dichromate ion.

    These solved questions provide the formula for a compound formed when sodium reacts with dichromate and the number of oxygen atoms in a dichromate ion.

    Frequently asked questions on dichromate formula

    1: What are the formulas for dichromate?

    Answer: The formulas for dichromate can refer to two different chemical species: the dichromate ion and the dichromate compound. Here are the formulas for both:

    – Dichromate Ion:

    The formula for the dichromate ion is Cr2O72-. It consists of two chromium atoms (Cr) bonded to seven oxygen atoms (O) in a linear arrangement.

    – Dichromate Compound:

    The formula for a dichromate compound will depend on the specific compound formed. It usually involves a metal cation combined with the dichromate ion. For example:

    -Sodium Dichromate: Na2Cr2O7

    -Potassium Dichromate: K2Cr2O7

    -Calcium Dichromate: CaCr2O7

    These are just a few examples, and various other metal cations can combine with the dichromate ion to form different dichromate compounds.

    It’s important to note that the dichromate ion, Cr2O72-, is a polyatomic ion that can combine with different cations to form various dichromate compounds.

    2: What is the formula used in the dichromate experiment?

    Answer: In a dichromate experiment, the formula often refers to the chemical reaction or equation being studied rather than a specific compound. The most commonly encountered dichromate experiment involves the reaction of a reducing agent with the dichromate ion (Cr2O72-) in an acidic solution. The balanced chemical equation for this reaction is typically represented as follows:

    Cr2O72- + 3e + 14H+ → 2Cr3+ + 7H2O

    In this equation, the dichromate ion (Cr2O72-) acts as an oxidizing agent, accepting three electrons (3e) and undergoing reduction to form chromium(III) ions (Cr3+). The hydrogen ions (H+) from the acidic solution are also involved in the reaction, and water (H2O) is formed as a product.

    This experiment is commonly used to determine the reducing power or reducing capacity of a given substance by measuring the amount of dichromate ion reduced in a titration or colorimetric analysis. The dichromate solution’s concentration is usually standardized using a primary standard reducing agent, such as ferrous ammonium sulfate (FeSO4(NH4)2SO4·6H2O), which is known to be stoichiometrically equivalent to the dichromate ion.

    3: How is dichromate formed?

    Answer: Dichromate (Cr2O72-) is typically formed by the reaction of chromate (CrO42-) with an oxidizing agent or under specific chemical conditions. The conversion of chromate to dichromate involves a change in the oxidation state of chromium.

    One common method for the formation of dichromate is through the addition of acid to a chromate solution. When a strong acid, such as sulfuric acid (H2SO4), is added to a chromate solution, the following reaction occurs:

    2 CrO42-+ 2H+ → Cr2O72- + H2O

    In this reaction, two chromate ions (CrO42-) react with two hydrogen ions (H+) to form one dichromate ion (Cr2O72-) and water (H2O).

    Another way to form dichromate is through the reaction of chromium(III) compounds with strong oxidizing agents, such as hydrogen peroxide (H2O2) or concentrated nitric acid (HNO3). The reaction involves the oxidation of chromium(III) to chromium(VI), resulting in the formation of dichromate.

    It’s important to note that the formation of dichromate is highly dependent on the specific reaction conditions and the presence of appropriate reactants. Controlling factors such as pH, temperature, and the choice of oxidizing agents is crucial in the synthesis of dichromate compounds.

    4: What is Cr2O72- known as?

    Answer: Cr2O72- is known as the dichromate ion.

    5: Is dichromate acidic or basic?

    Answer: The chromate ion is the predominant species in alkaline solutions, but dichromate can become the predominant ion in acidic solutions.

    6: What is Valency of Cr2O7?

    Answer: The valency of the dichromate ion (Cr2O72-) is 2. This means that the dichromate ion can form two bonds or combine with two other ions or atoms.

    7: How to balance Cr2O7?

    Answer: Balancing the equation involving dichromate ion (Cr2O72-) requires considering the oxidation states and ensuring that the number of atoms on both sides of the equation is equal. For example, if balancing the equation in an acidic medium, the following steps can be followed:

    1. a) Determine the oxidation states of chromium (Cr) and oxygen (O) in the dichromate ion.
    2. b) Balance the oxygen atoms by adding water (H2O) molecules.
    3. c) Balance the hydrogen atoms by adding hydrogen ions (H+).
    4. d) Balance the charge by adding electrons (e) to the appropriate side of the equation.
    5. e) Finally, balance the chromium atoms by adjusting the coefficients in front of the reactants and products.

    8: What is the colour of Cr2O7?

    Answer: The color of the dichromate ion (Cr2O72-) is orange. It exhibits a vibrant orange color, which is often used as a visual indicator in certain chemical reactions. The orange color is attributed to the electronic transitions that occur within the dichromate ion when it absorbs and reflects light in the visible spectrum.

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