| Galvanic cell |
a device in which chemical energy from a spontaneous redox
reaction is changed to electrical energy that can be used to do work |
| Galvanizing |
a process in which steel is coated with zinc to prevent
corrosion |
Gamma ray
|
a high-energy photon |
| Gangue |
the impurities (such as clay or sand) in an ore |
| Gay-Lussac's Law |
At constant temperature and pressure, the volumes of the
gases involved in chemical reactions have ratios of small whole numbers |
| Geiger-Miller counter (Geiger counter) |
an instrument that measures the rate of radioactive decay
based on the ions and electrons produced as a radioactive particle passes through a
gas-filled chamber |
| Geometrical Isomers |
Stereoisomers in which similar groups are located either on
the same side of a molecule (cis) or on opposite sides (trans) |
| Glass |
an amorphous solid obtained when silica is mixed with other
compounds, heated above its melting point, and then cooled rapidly |
| Glass electrode |
an electrode for measuring pH from the potential difference
that develops when it is dipped into an aqueous solution containing H+ ions |
| Glycosidic linkage |
a C-O-C bond formed between the rings of two cyclic
monosaccharides by the elimination of water |
| Graham's law of effusion |
the rate of effusion of a gas is inversely proportional to
the square root of the mass of its particles |
| Greenhouse effect |
a warming effect exerted by the earth's atmosphere
(particularly CO2 and H2O) due to thermal energy retained by
absorption of infrared radiation |
| Ground state |
the lowest possible energy state of an atom or molecule |
| Group (of the periodic table) |
a vertical column of elements having the same valence
electron configuration and showing similar properties |
| Haber process |
the manufacture of ammonia from nitrogen and hydrogen,
carried out at high pressure and high temperature with the aid of a catalyst |
| Half-cell |
One electrode and its accompanying solution in a voltaic cell |
| Half-life (of a radioactive sample) |
the time required for the number of nuclides in a radioactive
sample to reach half of the original value |
| Half-life (of a reaction) |
the time required for a reactant to reach half of its
original concentration |
| Half-reactions |
the two parts of an oxidation-reduction reaction, one
representing oxidation, the other reduction |
| Halogen |
a Group 7A element |
| Halogenation |
the addition of halogen atoms to unsaturated hydrocarbons |
| Hard water |
water from natural sources that contains relatively large
concentrations of calcium and magnesium ions |
| Heat |
energy transferred between two objects due to a temperature
difference between them |
| Heat capacity |
the amount of energy required to raise the temperature of an
object by one degree Celsius |
| Heat of fusion |
the enthalpy change that occurs to melt a solid at its
melting point |
| Heat of hydration |
the enthalpy change associated with placing gaseous molecules
or ions in water; the sum of the energy needed to expand the solvent and the energy
released from the solvent-solute interactions |
| Heat of solution |
the enthalpy change associated with dissolving a solute in a
solvent; the sum of the energies Deeded to expand both solvent and solute in a solution
and the energy released from the solvent-solute interactions |
| Heat of vaporization |
the energy required to vaporize one mole of a liquid at a
pressure of one atmosphere |
| Heating curve |
a plot of temperature versus time for a substance where
energy is added at a constant rate |
| Heisenberg uncertainty principle |
a principle stating that there is a fundamental limitation to
how precisely both the position and momentum of a particle can be known at a given time |
| Heme |
an iron complex |
| Hemoglobin |
a biomolecule composed of four myoglobinlike
units (proteins plus heme) that can bind and transport four oxygen molecules in the blood |
| Henderson-Hasselbalch equation |
an equation giving the relationship between the pH of an
acid-base system and the concentrations of base and acid |
| Henry's Law |
The solubility of a gas in a liquid is proportional to the
partial pressure of the gas above the liquid |
| Hess's law |
in going from a particular set of reactants to a
particular set of products, the enthalpy change is the same
whether the reaction takes place in one step or in a series of
steps; in summary, enthalpy is a state function |
| Heterocyclic Molecule |
A cyclic carbon compound containing atoms other than carbon
in the ring |
| Heterogeneous equilibrium |
an equilibrium involving reactants and/or products in more
than one phase |
| Heterogeneous |
Having nonuniform composition |
| Heterogeneous Catalyst |
A catalyst, often a solid, that is not present in the same
phase as the reactants and products |
| Heterogeneous Equilibrium |
An equilibrium in which more than one phase is present |
| Hexagonal closest packed structure |
a structure composed of closest packed spheres with an ababab
arrangement of layers; the unit cell is hexagonal |
| Homogeneous |
Having uniform composition |
| Homogeneous Catalyst |
A catalyst present in the same phase as the reactants and
products |
| Homogeneous equilibrium |
an equilibrium system where all reactants and products are in
the same phase |
| Homopolymer |
a polymer formed from the polymerization of only one type of
monomer |
| Hund's Rule |
The lowest energy state of an atom is that in which electrons
occupy different orbitals of the same energy with parallel spins to the extent possible |
| Hybrid Orbitals |
Equivalent atomic orbitals resulting from mixing different
atomic orbitals of an atom The hybrid orbitals have characteristics dependent on the
particular combination of atomic orbitals |
| Hybridization |
a mixing of the native orbitals on a given atom to form
special atomic orbitals for bonding |
| Hydration |
the interaction between solute particles and water molecules |
| Hydridic |
Exhibiting the character of the hydride ion |
| Hydride |
a binary compound containing hydrogen The hydride ion, H-,
exists in ionic hydrides The three classes of hydrides are covalent, interstitial, and
ionic |
| Hydrocarbon |
a compound composed of carbon and hydrogen |
| Hydrogen bonding |
An exceptionally strong dipoledipole attraction between an F,
O, or N atom and a hydrogen atom attached to a second F, O, or N atom |
| Hydrogenation reaction |
a reaction in which hydrogen is added, with a catalyst
present, to a carbon-carbon multiple bond |
| Hydrohalic acid |
an aqueous solution of a hydrogen halide |
| Hydronium Ion |
The hydrated proton, H+; the conjugate acid of water |
| Hydrometallurgy |
a process for extracting metals from ores by use of aqueous
chemical solutions Two steps are involved: selective leaching and selective precipitation |
| Hydrophilic |
Having an attraction to water |
| Hydrophobic |
Having no attraction to water |
| Hypothesis |
one or more assumptions put forth to explain the observed
behavior of nature |
