H

Heavy Water

D₂O CAS 7789-20-0
Quick Reference
Formula / NotationD₂O
CAS Number7789-20-0
Also Known AsDeuterium oxide, deuterated water, D₂O, oxide deuterium

What is Heavy Water?

Heavy water is water in which both hydrogen atoms are replaced by deuterium (²H or D), the stable isotope of hydrogen with one proton and one neutron. Its chemical formula is D₂O. Heavy water is about 10% denser than ordinary water and has slightly higher melting and boiling points. It is used as a neutron moderator in some nuclear reactors and as a tracer in chemical and biological research.

Formula & Notation

D₂O

Other Names / Synonyms: Deuterium oxide, deuterated water, D₂O, oxide deuterium

Properties & Characteristics

Molecular weight: 20.03 g/mol. Density: 1.1056 g/cm³ at 25°C. Melting point: 3.81°C. Boiling point: 101.4°C. Natural abundance: 0.0156% of water. Neutron absorption cross-section much lower than ordinary water. Slightly different reaction rates from H₂O (kinetic isotope effect). Miscible with ordinary water.

Uses & Applications

CANDU nuclear reactor moderator and coolant. Neutron moderation in research reactors. NMR spectroscopy solvent (deuterated solvents). Isotope labeling in chemical and biological research. Metabolic rate studies. Neutron scattering experiments. Production of deuterium and tritium.

Safety Information

Not radioactive — chemically similar to water. If consumed in large amounts (>20% of body water), can disrupt cellular processes and potentially be lethal — disrupts enzymatic reactions. Occupational exposure to high concentrations may cause dizziness. Standard radiation safety procedures apply in reactor contexts.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Heavy Water
Formula D₂O
CAS Number 7789-20-0
Synonyms Deuterium oxide, deuterated water, D₂O, oxide deuterium

Frequently Asked Questions

Heavy water is water in which both hydrogen atoms are replaced by deuterium (²H or D), the stable isotope of hydrogen with one proton and one neutron. Its chemical formula is D₂O. Heavy water is about 10% denser than ordinary water and has slightly higher melting and boiling points. It is used as a neutron moderator in some nuclear reactors and as a tracer in chemical and biological research.

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