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In chemistry, the mole fraction or molar fraction, also called mole proportion or molar proportion, is a quantity defined as the ratio between the amount of a constituent substance, n i (expressed in unit of moles, symbol mol), and the total amount of all constituents in a mixture, n tot (also expressed in moles): [1]
The term stoichiometry is also often used for the molar proportions of elements in stoichiometric compounds (composition stoichiometry). For example, the stoichiometry of hydrogen and oxygen in H 2 O is 2:1. In stoichiometric compounds, the molar proportions are whole numbers.
Another application is in radiochemistry, where this may refer to isotopic ratios or isotopic abundances.Mathematically, the isotopic abundance is = , where N i are the number of atoms of the isotope of interest and N tot is the total number of atoms, while the atomic ratio is
The sum of molar concentrations gives the total molar concentration, namely the density of the mixture divided by the molar mass of the mixture or by another name the reciprocal of the molar volume of the mixture. In an ionic solution, ionic strength is proportional to the sum of the molar concentration of salts.
Two binary solutions of different compositions or even two pure components can be mixed with various mixing ratios by masses, moles, or volumes. The mass fraction of the resulting solution from mixing solutions with masses m 1 and m 2 and mass fractions w 1 and w 2 is given by:
Historically, the mole was defined as the amount of substance in 12 grams of the carbon-12 isotope.As a consequence, the mass of one mole of a chemical compound, in grams, is numerically equal (for all practical purposes) to the mass of one molecule or formula unit of the compound, in daltons, and the molar mass of an isotope in grams per mole is approximately equal to the mass number ...
In physical chemistry, Henry's law is a gas law that states that the amount of dissolved gas in a liquid is directly proportional at equilibrium to its partial pressure above the liquid. The proportionality factor is called Henry's law constant .
Redfield discovered the remarkable congruence between the chemistry of the deep ocean and the chemistry of living things such as phytoplankton in the surface ocean. Both have N:P ratios of about 16:1 in terms of atoms. When nutrients are not limiting, the molar elemental ratio C:N:P in most phytoplankton is 106:16:1. Redfield thought it wasn't ...