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Home >> Inorganic Chemistry Dictionary >> Rare Earth Salts - Relative Molecular Mass
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Radium (Ra)
The only radioactive element of group 2 (alkaline earths). It is used to produce alloys, radio tubes and photoelectric cells.
Radium carbonate(RaCO3)
Obtained by adding ammonium carbonate to a radium salt solution or by fusing radium sulphate and sodium carbonate. It is insoluble in water.
Radium hydroxide [Ra(NO)2]
Obtained when radium reacts with water.
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Radium nitrate (Ra(NO3)2]
Prepared by dissolving radium carbonate in nitric acid and crystallizing from the solution.
Radium sulphate
RaSO4, water-insoluble, radioactive, poisonous, white crystals; used in medicine.
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Radon (rn)
It is an element of group 18 (Z= 86). It is used in radiography.
Rare gases
The 18th element in the periodic table (noble gases) are rare gases because their pressure in atmosphere is very small, e.g., He, Ne, Ar, Kr, Xe, Rn.
Rare-earth salts
Salts derived from monazite, and with rare earths in similar proportions as in monazite; contains La, Ce, Pr, Nd, Sm, Gd, and Y as acetates, carbon ates, chlorides, fluorides, nitrates, sulphates, and so on.
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Reagent
Refers to a compound that reacts with another. The term is usually used for common laboratory chemical¾sodium hydroxide, hydrochloric acid, etc., used for experiment and analysis.
Redox indicator
a compound which undergoes a definite colour change during its reversible oxidation or reduction, e.g. methylene blue is colourless when reduced and blue when oxidized.
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Refining
Refers to the process of purifying substance or extracting substances from mixtures.
Refractory
A material not damaged by heating to high temperatures. Such materials are made into bricks and used for lining furnaces, etc.
Relative atomic mass
Symbol; A1, the ratio of the average mass per atom of the naturally occurring element to 1/12 of the mass of an atom of nuclide 12C. It was formerly called atomic weight.
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Relative formula mass
The mass of one mole of a chemical compound or elements expressed in grams, calculated from the relative atomic masses for each of the atoms in the formula.
Relative molecular mass
The mass of one molecule of a compound calculated by adding together the relative atomic masses of each atom within the molecule. For example.
RMM of carbondioxide (CO2) =12 + 2 x 16 = 44
RMM of ammonia (NH3)= 14 + 3 x 1 = 17.
Resonance
The behaviour of many compounds cannot be adequately explained by a single structure using simple single and double bonds. The bonding electrons of the compound have a different distribution in the molecules. The actual bonding in the molecule can be regarded as a hybrid of two or more conventional forms of the molecule, called resonance forms or canonical forms. The result is a resonance hybrid.
Reverse osmosis
A process of separating solute from a solution by making the solvent to flow through a membrane at apressure higher than the normal osmotic pressure. Used for concentration and dehydration of food products (e.g., milk and juices), for treatment of recycle water in chemical plants, etc.
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