Definition

Noun: A monohydrate is a specific type of hydrate, which is a compound formed by the chemical combination of a substance with water. A monohydrate contains exactly one molecule of water (H₂O) for each molecule of the primary compound or salt.

Usage

The term is used primarily in chemistry and material science to specify the precise water content in a crystalline solid. It indicates a 1:1 molar ratio between the host compound and water of crystallization. - It is often part of a compound's systematic name (e.g., calcium sulfate monohydrate). - The presence or absence of water molecules (as in a monohydrate vs. an anhydrous form) can significantly affect a substance's physical and chemical properties.

Examples

• The common plaster of Paris is calcium sulfate hemihydrate, whereas the more stable form used in setting casts is calcium sulfate monohydrate.
• Copper(II) sulfate exists as a blue crystalline monohydrate (CuSO₄·H₂O) under certain conditions.
• When writing a chemical formula for a monohydrate, a centered dot is used, as in Na₂CO₃·H₂O (sodium carbonate monohydrate).

Advanced Usage

• Stoichiometry: In precise chemical contexts, "monohydrate" specifies the stoichiometry of hydration, crucial for reactions and calculations where water content affects molar mass and yield.
• Pharmaceuticals: Many active pharmaceutical ingredients (APIs) are manufactured and stored as specific hydrates (like a monohydrate) because this form often provides better stability, solubility, or shelf life than other forms.

Variants and Related Words

• Hydrate (n.): The general class of compounds containing water molecules combined in a definite ratio.
• Anhydrous (adj.): Describing a substance that contains no water molecules.
• Dihydrate (n.): A hydrate containing two molecules of water per formula unit.
• Hemihydrate (n.): A hydrate containing one-half molecule of water per formula unit (e.g., CaSO₄·½H₂O).

Synonyms

• Hydrated compound (specific type)
• Crystalline hydrate (specific type)

Note: There are no specific idioms or phrasal verbs associated with this technical term.

Noun

1. a hydrate that contains one molecule of water per molecule of the compound