| Qualitative Analysis |
The determination of what ions or elements are
present in a material |
| Quantization |
the concept that energy can occur only in
discrete units called quanta |
| Quantum |
A small, discrete unit of energy |
| Quantum Numbers |
Numbers that govern the magnitude of quantized
properties, such as energy |
| Rad |
a unit of radiation dosage corresponding to 10-2
j of energy deposited per kilogram of tissue (from radiation absorbed dose) |
| Radiant Energy |
Energy associated with electromagnetic radiation |
| Radioactive decay (radioactivity) |
the spontaneous decomposition of a nucleus to
form a different nucleus |
| Radiocarbon dating (carbon-14 dating) |
a method for dating ancient wood or cloth based
on the rate of radioactive decay of the nuclide 14C |
| Radiotracer |
a radioactive nuclide, introduced into an
organism for diagnostic purposes, whose pathway can be traced by monitoring its
radioactivity |
| Random error |
an error that has an equal probability of being
high or low |
| Raoult's law |
the vapor pressure of a solution is directly
proportional to the mole fraction of solvent present |
| Rate constant |
the proportionality constant in the relationship
between reaction rate and reactant concentrations |
| Rate of decay |
the change in the number of radioactive nuclides
in a sample per unit time |
| Rate-determining step |
the slowest step in a reaction mechanism, the one
determining the overall rate |
| Rate Equation |
The mathematical statement of the relationship
between the rate of a reaction and reactant concentrations |
| Rate law (differential rate law) |
an expression that shows how the rate of reaction
depends on the concentration of reactants |
| Reactants |
The starting materials in a chemical reaction |
| Reaction mechanism |
The sequence of steps, that is, of elementary
processes, through which reactants form products |
| Reaction quotient |
a quotient obtained by applying the law of mass
action to initial concentrations rather than to equilibrium concentrations |
| Reaction rate |
the change in concentration of a reactant or
product per unit time |
| Reactor core |
the part of a nuclear reactor where the fission
reaction takes place |
| Recrystallization |
The process of dissolving a solid in a solvent
followed by crystallization as a method of purification of the solid |
| Reducing Agent |
A substance that loses electrons during a
reaction, causing another substance to be reduced |
| Reduction |
a decrease in oxidation state (a gain of
electrons) |
| Reduction of Ores |
Reduction of the metallic compound to the free
metal |
| Refining of Metals |
The purification steps taken to prepare a metal
for practical use |
| Rem |
a unit of radiation dosage that accounts for both
the energy of the dose and its effectiveness in causing biological damage (from roentgen
equivalent for man) |
| Representative Elements |
Elements in the A groups of the periodic table s
and p blocks, which form families of similar elements in vertical columns |
| Resonance |
The phenomenon exhibited by some molecules for
which more than one Lewis structure can be written Molecules exhibiting resonance have
properties, such as stability and bond length, that are not those to be expected for the
molecule represented by any of the Lewis structures |
| Resonance Energy |
The energy difference between the actual hybrid
structure of a molecule and the hypothetical contributing structures |
| Resonance Hybrid |
The actual structure of a molecule exhibiting
resonance A resonance hybrid cannot be represented by a single Lewis structure but is
depicted as a combination of two or more structures |
| Reverse osmosis |
the process occurring when the external pressure
on a solution causes a net flow of solvent through a semipermeable membrane from the
solution to the solvent |
| Reversible process |
a cyclic process carried out by a hypothetical
pathway, which leaves the universe exactly the same as it was before the process No real
process is reversible |
| Roasting |
a process of converting sulfide minerals to
oxides by heating in air at temperatures below their melting points |
| Root mean square velocity |
the square root of the average of the squares of
the individual velocities of gas particles |
| Rotational Spectra |
Absorption spectra resulting from the excitation
of molecules between rotational energy states; microwave spectra |
