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The sum of the molalities of all solute particles in a solution.

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Polarimeter

A device used to measure optical activity.

Valence Bond Theory

Assumes that covalent bonds are formed when atomic orbitals on different atoms overlap and the electrons are shared.

Saccharate

A compound formed by interaction of sucrose with a metallic oxide, usually lime, and useful in the purification of sugar.

 

Graham's Law

The rates of effusion of gases are inversely proportional to the square roots of their molecular weights or densities.

Oxidation-reduction Reactions

Reactions in which oxidation and reduction occur, also called redox reactions.

Clay

A class of silicate and aluminosilicate minerals with sheet-like structures that have enormous surface areas that can absorb large amounts of water.

Alkyl Group

A group of atoms derived from an alkane by the removal of one hydrogen atom.

Plasma

A physical state of matter which exists at extremely high temperatures in which all molecules are dissociated and most atoms are ionized.

Quantum Numbers

Numbers that describe the energies of electrons in atoms, derived from quantum mechanical treatment.

Semiconductor

A substance that does not conduct electricity at low temperatures but does so at higher temperatures.

Colloid

A heterogeneous mixture in which solute-like particles do not settle out.

Alkylbenzene

A compound containing an alkyl group bonded to a benzene ring.

Zinc

Discovered: known in India and China before 1500 and to the Greeks and Romans before 20 BC as the copper-zinc alloy brass
Origin: The name is derived from the German ‘Zink’.
Atomic no: 30
Mass No: 65
Description: A grey metal with a blue tinge. World production exceeds 7 million tons a year, and it is used to galvanise iron to prevent it rusting. It is also employed in alloys and batteries, and as zinc oxide to stabilise rubber and plastics. Zinc is essential for all living things, and is important for growth and development. The average human body contains about 2.5 grams and takes in about 15 milligrams per day. Some foods have above average levels of zinc, including herring, beef, lamb, sunflower seeds and cheese.

Fossil Fuels

Substances consisting largely of hydrocarbons, derived from decay of organic materials under geological conditions of high pressure and temperature (metamorphism) include coal, petroleum, natural gas, peat and oil shale.  For further information see Fuel Chemistry

Law of Definite Proportions (Law of Constant Composition)

The law stating that a pure substance will always have the same percent by weight. Different samples of a pure compound always contain the same elements in the same proportions by mass.

Oxidation

An algebraic increase in the oxidation number, may correspond to a loss of electrons.

Radioactive Tracer

A small amount of radioisotope replacing a nonradioactive isotope of the element in a compound whose path (for example, in the body) or whose decomposition products are to be monitored by detection of radioctivity, also called a radioactive label.

Emulsifying Agent

A sustance that coats the particles of the dispersed phase and prevents coagulation of colloidal particles, an emulsifier.

Weak Field Ligand

A Ligand that exerts a weak crystal or ligand field and ge- nerally forms high spin complexes with metals.

Semipermable Membrane

A thin partition between two solutions through which certain molecules can pass but others cannot.