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Abbreviated list of quantities, units and symbols in physical chemistry

 1. Base SI units and physical quantities

A physical quantity is the product of a numerical value (a pure number) and a unit.

Physical quantities are organized in a dimensional system built upon seven base quantities. The International System of Units (SI) is based on the seven base units having the same dimensions as the associated physical quantities. Their names and symbols are as follows:

Base Physical Quantity Symbol for Quantity Name of SI Unit Symbol for SI Unit
length l metre m
mass m kilogram kg
time t second s
electric current I ampere A
thermodynamic temperature T kelvin K
amount of substance n mole mol
luminous intensity Iv candela cd

The symbol for a physical quantity is a single letter of the Latin or Greek alphabet printed in italic (sloping) type. It may be modified by subscripts and/or superscripts of specified meaning, or further characterized in particular cases through annotations in parenthesies put directly behind the symbol. The symbol for a unit is printed in roman (upright) type. Neither symbol should be followed by a full stop (period).

The physical quantity 'amount of substance' or 'chemical amount' is proportional to the number of elementary entities - specified by a chemical formula - of which the substance is composed. The proportionality factor is the reciprocal of the Avogadro constanct L (6.022 x 1023 mol-1). The amount of substance should no longer be called 'number of moles'.

Examples of relations between "amount of substance" and other physical quantities:

2 moles of N2 contain 12.044-x-1023 molecules of N2, amount of N2 = n(N2) = number of N2 molecules/L;

1.5 moles of Hg2Cl2 have a mass of 708.13 g;

1 mole of photons with frequency 1014 Hz has an energy of 39.90 kJ;

1 mole of electrons, e-, contains 6.022-x-1023 electrons, has a a mass of 5.468-x-10-7 kg, and a charge of -96.49 kC.

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