Sulfur Dioxide Reduction of Dichromate

Cr₂O₇²⁻ + 3SO₂ + 2H⁺ → 2Cr³⁺ + 3SO₄²⁻ + H₂O

Overview

Sulfur dioxide reduces orange dichromate to green chromium(III) while being oxidized to sulfate. This reaction changes the solution color from orange to green and is used as a test for SO₂ gas. Cr(VI) gains 3 electrons per atom while S(IV) loses 2 electrons per atom.

Participants

Role	Substance	Coefficient	State
Reactant	Sulfur Dioxide SO₂	3	(g)
Product	Water H₂O	1	(l)

Everyday Example

Dichromate-impregnated paper is used as a sensitive test for sulfur dioxide gas, turning from orange to green in its presence.

Industrial Importance

This reaction is relevant to flue gas monitoring, environmental SO₂ detection, and understanding chromium redox chemistry in industrial processes.

Properties

Type: Redox
Reversible: No
Energy: Exothermic
ΔH: -850.0 kJ/mol

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Frequently Asked Questions

What is the equation for Sulfur Dioxide Reduction of Dichromate?

The balanced equation is: Cr₂O₇²⁻ + 3SO₂ + 2H⁺ → 2Cr³⁺ + 3SO₄²⁻ + H₂O.

What type of reaction is Sulfur Dioxide Reduction of Dichromate?

Sulfur Dioxide Reduction of Dichromate is a redox reaction.

Is Sulfur Dioxide Reduction of Dichromate exothermic or endothermic?

Sulfur Dioxide Reduction of Dichromate is exothermic (releases energy). The enthalpy change (ΔH) is -850.0 kJ/mol.