Chemistry terms starting with H

Homologous Series Organic Chemistry Dimensionless A family of compounds sharing the same functional group and general formula, with successive members differing by CH₂. differ by −CH₂−

Hormone Biochemistry & Polymer Chemistry mol/L A chemical messenger released by one tissue that regulates the activity of cells elsewhere in the body.

Hund's Rule of Maximum Multiplicity Atomic Structure & Periodicity Dimensionless The rule that electrons occupy degenerate orbitals singly with parallel spins before any orbital is doubly occupied. maximise total spin S

Hybridisation Chemical Bonding & Molecular Structure Dimensionless The mixing of atomic orbitals on the same atom to form an equal number of new, equivalent orbitals suited to bonding.

Hydrate Foundations of Chemistry Dimensionless A crystalline compound in which a definite number of water molecules is incorporated into the lattice. MX·nH₂O

Hydrate Isomerism Inorganic & Coordination Chemistry Dimensionless Isomerism arising from water molecules occupying either the coordination sphere or lattice positions outside it.

Hydration Energy Solutions & Colligative Properties kJ/mol The energy released when one mole of gaseous ions is surrounded by water molecules to form a dilute aqueous solution. ΔH_hyd ∝ z / r

Hydration Reaction Stoichiometry & Chemical Reactions Dimensionless The addition of water across a multiple bond or the incorporation of water into a crystal lattice. C=C + H₂O → C(OH)–CH

Hydrocarbon Organic Chemistry Dimensionless A compound composed exclusively of carbon and hydrogen. CₓH_y

Hydrogen Bond Chemical Bonding & Molecular Structure kJ/mol A strong dipole interaction between a hydrogen atom bonded to N, O or F and a lone pair on another such atom. X–H···Y (X, Y = N, O, F)

Hydrogen–Oxygen Fuel Cell Electrochemistry & Redox V A fuel cell in which hydrogen is oxidised at the anode and oxygen reduced at the cathode, producing only water. 2H₂ + O₂ → 2H₂O, E° = 1.23 V

Hydrolysis Stoichiometry & Chemical Reactions Dimensionless A reaction in which a bond is cleaved by water, with the H and OH fragments adding to the two products. AB + H₂O → AOH + BH

Hydrolysis Constant Acids, Bases & Salts mol/L The equilibrium constant for the hydrolysis of a salt ion in water. Kh = Kw / Ka (anion)

Hyperconjugation Organic Chemistry kJ/mol The stabilising delocalisation of electrons from a sigma C–H bond into an adjacent empty or partly filled p orbital.

Hypertonic Solution Solutions & Colligative Properties atm A solution with a higher osmotic pressure than the one it is compared with, drawing water out of the more dilute side. π_solution > π_cell

Hypotonic Solution Solutions & Colligative Properties atm A solution with a lower osmotic pressure than the one it is compared with, so water flows into the more concentrated side. π_solution < π_cell

Hückel's Rule Organic Chemistry Dimensionless The rule that a planar cyclic conjugated system is aromatic if it contains 4n + 2 pi electrons. 4n + 2 π electrons

Terms starting with H