Definition

Noun: * An unstable acid known only in solution and as chromate salts: A strong, corrosive, and oxidizing acid with the formula H₂CrO₄. It is not isolatable as a pure substance but exists in equilibrium with dichromic acid (H₂Cr₂O₇) in aqueous solutions. It is a powerful oxidizing agent.

Usage

• Chromic acid is primarily used in laboratory settings and industrial processes. It is commonly referenced in the context of its solutions or its salts (chromates and dichromates).
• It is often mentioned in procedures for cleaning laboratory glassware, though its use has declined due to its high toxicity and environmental hazards.
• It is a key reagent in oxidation reactions in organic chemistry.

Examples

• The glassware was soaked in a chromic acid bath for cleaning.
• Chromic acid oxidation converts primary alcohols to carboxylic acids.
• Due to its carcinogenic nature, handling chromic acid requires strict safety protocols.

Advanced Usage

• "Chromic acid solution": The typical form in which this acid is used, often referring to a mixture of a dichromate salt (like sodium dichromate) with a strong acid (like sulfuric acid).
  • The old chromic acid solution was prepared by dissolving potassium dichromate in concentrated sulfuric acid.
• "Chromic acid anodizing": An industrial electrochemical process that uses a chromic acid electrolyte to produce a corrosion-resistant oxide layer on aluminum.
  • Aircraft components often undergo chromic acid anodizing for protection.

Variants and Related Words

• Chromate (n): A salt or ester of chromic acid, containing the anion CrO₄²⁻.
  • Sodium chromate is a yellow crystalline compound.
• Dichromate (n): A salt containing the dichromate ion, Cr₂O₇²⁻, which is in equilibrium with chromate in acidic solutions.
  • Potassium dichromate is a common oxidizing agent.

Synonyms

• Oxidizing acid: A general descriptive term for acids like chromic acid that readily accept electrons in chemical reactions.

Important Notes (Safety and Context)

• Chromic acid and its compounds are highly toxic, carcinogenic, and severe environmental pollutants. Their use is heavily regulated.
• In many contexts, the term "chromic acid" may refer practically to a cleaning solution made from sodium or potassium dichromate and sulfuric acid, rather than the pure, hypothetical H₂CrO₄.

Noun

1. an unstable acid known only in solution and as chromate salts