The equivalent (Eq or eq) is a reasonably common
measurement unit used in
chemistry and the
biological sciences. It is a measure of a
substance's ability to combine with other substances. It is frequently used in the context of
normality.The equivalent is formally defined as the
mass in
grams of a substance which will react with 6.022 x 1023
electrons. (This is
Avogadro's Number, which is the number of particles in a
mole). Another, slightly less precise, definition describes the equivalent as the number of grams of a substance that will react with a gram of free
hydrogen. (This is practically true, since a gram of hydrogen is very close to a mole of hydrogen, and free hydrogen has one spare electron; hence one gram of hydrogen is effectively equivalent to 6.022 x 1023 electrons.)
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