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Chemistry Dictionary Terminology "A"
Chemistry Dictionary Terminology  "H"

Haber Process
A process for the catalyzed industrial production of ammonia from N2 and H2 at high temperature and pressure.
Half-Cell
Compartment in which the oxidation or reduction half-reaction occurs in a voltaic cell.
Half-Life
The time required for half of a reactant to be converted into product(s).
The time required for half of a given sample to undergo radioactive decay.
Half-Reaction
Either the oxidation part or the reduction part of a redox reaction.
Halogens
Group VIIA elements: F, Cl, Br, I
Hard Water
Water containing Fe3+, Ca2+, and Mg2+ ions, which forms precipates with soap.
Heat
A form of energy that flows between two samples of matter because of their differences in temperature.
Heat Capacity
The amount of heat required to raise the temperature of a body (of any mass) one degree Celsius.
Heat of Condensation
The amount of heat that must be removed from one gram of a vapor at it's condensation point to condense the vapour with no change in temperature.
Heat of Crystallization
The amount of heat that must be removed from one gram of a liquid at its freezing point to freeze it with no change in temperature.
Heat of Fusion
The amount of heat required to melt one gram of solid at its melting point with no change in temperature. Usually expressed in J/g. The molar heat of fusion is the amount of heat required to melt one mole of a solid at its melting point with no change in temperature and is usually expressed in kJ/mol.
Heat of Solution
The amount of heat absorbed in the formation of solution that contains one mole of solute; the value is positive if heat is absorbed (endothermic) and negative if heat is released (exothermic).
Heat of Vaporization
The amount of heat required to vaporize one gram of a liquid at its boiling point with no change in temperature. Usually expressed in J/g. The molar heat of vaporization is the amount of heat required to vaporize one mole of liquid at its boiling point with no change in temperature and usually expressed ion kJ/mol.
Heavy Water
Water containing deuterium, a heavy isotope of hydrogen.
Heisenberg Uncertainty Principle
It is impossible to determine accurately both the momentum and position of an electron simultaneously.
Henry's Law
The pressure of the gas above a solution is proportional to the concentration of the gas in the solution.
Hess' Law of Heat Summation
The enthalpy change for a reaction is the same whether it occurs in one step or a series of steps.
Heterocyclic Amine
Amine in which the nitrogen is part of a ring.
For further information see Heterocyclic Chemistry
Heterogeneous Catalyst
A catalyst that exists in a different phase (solid, liquid or gas) from the reactants; a contact catalyst.
Heterogeneous Equilibria
Equilibria involving species in more than one phase.
Heterogeneous Mixture
A mixture that does not have uniform composition and properties throughout.
Heteronuclear
Consisting of different elements.
High Spin Complex
Crystal field designation for a