acidic hydrogen
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Definition
Noun: * Acidic Hydrogen: A hydrogen atom within an acid molecule that is capable of being released (donated) as a proton (H⁺ ion) when the acid dissociates in a solution. This hydrogen is typically bonded to an oxygen atom (as in -O-H) or, less commonly, directly to the central atom in the molecule.
Usage
This is a technical term used primarily in chemistry to describe the specific, reactive hydrogen atoms in an acid. It distinguishes the hydrogen(s) that contribute to acidity from other hydrogen atoms in the same molecule that are not acidic.
Examples
- In acetic acid (CH₃COOH), only the hydrogen atom in the -COOH group is an acidic hydrogen.
- Sulfuric acid (H₂SO₄) has two acidic hydrogens.
- To determine the equivalent weight of the acid, you must count the number of acidic hydrogens per molecule.
Advanced Usage
- The strength of an acid is related to how readily its acidic hydrogen dissociates.
- In polyprotic acids, the first acidic hydrogen is usually easier to remove than the subsequent ones.
Variants and Related Words
- Acidic (adjective): Having the properties of an acid; containing acid.
- Hydrogen Ion (noun): The H⁺ cation released when an acidic hydrogen dissociates.
- Proton (noun): In the context of acid-base chemistry, often used synonymously with hydrogen ion (H⁺).
Synonyms
- Acidic proton
- Ionizable hydrogen
Related Phrases / Concepts
- Acid Dissociation: The process where an acid releases its acidic hydrogen as a proton.
- Brønsted-Lowry Acid: A substance that donates a proton (an acidic hydrogen).
Noun
- a hydrogen atom in an acid that forms a positive ion when the acid dissociates