Amount of substance
The amount of substance ( mole outdated or number of moles ) with the formula sign is a basic parameter in the International System of Units ( SI) and is indirectly the number of particles of a material portion of. Particles can be here atoms, ions, molecules, formula units, or electrons. Symbols and particle X be specified as n or n X (X).
The unit of amount of substance is the mole, an SI base unit. An amount of mass of 1 mole ( n = 1) corresponds to about 6.022 · 1023 particles, see Avogadro constant. The Avogadro constant NA is the proportionality between the amount of substance and the number of particles N ( X):
Amount of substance and the derived variables such as amount of substance concentration, mole fraction and mole ratio are important in the stoichiometry. The use of the size molar shifts considerations of chemical reactions from the atomic or molecular level to ponderable masses of matter with very high number of particles.
For the amount of substance n X and the mass mX of a portion of matter of a substance and its molar mass X MX applies:
Calculation of amount of substance
The calculation of the amount of substance
From the crowd ...
The calculation of the mass is possible using the equation given above.
For example, the molar mass of water is 18 grams per mole 9 grams of water thus correspond to a material amount of 0.5 mol
From the volume ...
One mole of an ideal gas occupies a volume of Vm = 22.4 L / mol under standard conditions in approximation. This volume is called the molar standard volume ( molar volume ). The amount of substance is obtained directly from the volume.
Example: How many moles of oxygen correspond to 5 l?
Of the particle ...
Since the number of particles N is proportional to the amount of substance n ( the proportionality factor is the Avogadro constant NA = 6.022 · 1023/mol ), can be seen from the number of particles to calculate the amount of substance.
Example: Given N = 1025 particles.
From the concentration ...
Since the concentration cX (mol / l ) is a measure of concentration for solutions, which represents the amount of substance of a substance X in relation to the volume V of the solution, you can also expect them back on the amount.
Example: How many moles of sodium chloride are in 0.22 liters of a 0.6 molar solution of NaCl?