A radical is a stable group of atoms, which remain chemically
combined in the group that is unaltered in chemical reactions,
but which is usually incapable of independent existence.
Radioactivity is the spontaneous disintegration of an
unstable nucleus, by the emission of a small particle (i.e.
an alpha-particle or a beta-particle) or by the change of the
energy level of the nucleus by the emission of a gamma-ray.
Raoult's Law states that the vapour pressure of a solvent is
reduced in the presence of dissolved solute. The law applies
only to dilute solutions.
The reduction of the vapour pressure of a solvent containing
dissolved solute is proportional to the number of molecules of
solute and is independent of their nature.
The rate of migration is the speed at which the ions travel
through a solution during electrolysis.
Rates of reactions are the velocities with which chemical
Reaction with phosphorus pentachloride is a characteristic of
organic compounds containing a hydroxyl group and this reaction
is used to identify these compounds in organic analysis.
Reactants are the starting materials in a chemical reaction,
and during the course of the reaction, these are replaced by
a new set of materials called products.
Reaction mechanisms are the detailed step-by-step descriptions
of the progress of a chemical reactions. The exact sequence
for the breaking and making of bonds, and the electron transfers
which give rise to this process are described.
The reactivity of a metal is determined to a large extent by its
Redox reaction occur when Oxidation
and Reduction takes place
in the one reaction. If one substance loses electrons, or
atoms of oxygen or hydrogen, then another substance must
gain them. Redox reactions always involve the
swapping of electrons.
Redox titration's are volumetric determinations titration's in
which electrons are transferred from a Reducing
to an Oxidising Agent.
The same principle holds as in acid-base and Argentometric Titration's.
A reducing agent is a substance which reduces another substance.
Reduction is the process in which an atom or ion gains
electrons. This definition applies only to reactions
in which electron transfer occurs. Originally, reduction was
simply regarded as a chemical reaction with the loss of oxygen.
Reduction by carbon is an important method for the extraction of
metals from their ores.
Reforming is the conversion of straight chain
alkanes into branched chain alkanes by
cracking or by
catalytic reaction .
Relative atomic mass (i.e. relative atomic weight) is the ratio of
the average mass per atom of the naturally occurring form of an
element to the 1 / 12 part of the mass of a Carbon-12 atom.
The relative density, rd, of a substance is the ratio of the
density of the substance to the density of some
reference substance. For liquids or solids, the reference substance is
water. This quantity was formerly called Specific Gravity.
Relative molecular mass (i.e. molecular weight) is the ratio of
the average mass per molecule of the naturally occurring form of
an element or compound to the 1 / 12 part of the mass of the
carbon-12 atom. It is equal to the sum of the relative atomic
masses of all the atoms that comprise a molecule.
Resonance is the different arrangements of the bonds within a
molecule that explain the chemical properties of the molecule,
that cannot be accurately represented by a single structural
formula. The compounds have properties consistent with a
formula which is intermediate between all possible formulae.
For example in the structure of the cyclic hydrocarbon
Benzene, C6H6, there two arrangements
of the alternating single and double bonds within the ring structure which are
equally probable and give rise to identical chemical properties
Reverse osmosis is a process of obtaining pure water from saline water, as in a
unit. Pure water and the salt are separated by a semi-permeable membrane, by raising
the pressure of the salt water above the
Then, the solvent, water, is able to pass through the membrane, leaving the solute
(i.e. the dissolved salts) behind.
An Rf value of a substance is the ratio of the distance that the substance moves in a
to the distance that the solvent moves.
A ring is an arrangement of atoms in a molecule to form a closed
chain. Ring compounds may consist of
- an alicyclic ring structure (e.g. cyclohexane),
- an aromatic ring structure (e.g. benzene), or
- a fused ring structure (e.g. naphthalene).
Ring closures are chemical reactions in which one part
of a molecule reacts with another part of the same molecule
to form a ring structure. Examples of ring closures
include the formation of lactams and lactones.
Rochelle's Salt, (i.e. Sodium Potassium Tartate), KNaC4H4O6.4H20, is
a colourless crystalline salt.
Rust is a hydrated ferric oxide which has the approximate chemical
Start of Hypertext ....
Hypertext Copyright (c) 2000 Donal O'Leary. All Rights Reserved.