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In chemistry, a formula unit is the smallest unit of a non-molecular substance, such as an ionic compound, covalent network solid, or metal. [1] [2] It can also refer to the chemical formula for that unit. Those structures do not consist of discrete molecules, and so for them, the term formula unit is used.
Definition ≡ exactly equal ≈ approximately equal to โ (exactly) corresponds to (different types of quantity describing the same phenomenon) digits: indicates that digits repeat infinitely (e.g. 8.294 369 corresponds to 8.294 369 369 369 369...) (H) of chiefly historical interest
A closely related system is the International System of Electric and Magnetic Units, [18] which has a different unit of mass so that the formula for ๐′ is invalid. The unit of mass was chosen to remove powers of ten from contexts in which they were considered to be objectionable (e.g., P = VI and F = qE ).
Conversion and its related terms yield and selectivity are important terms in chemical reaction engineering.They are described as ratios of how much of a reactant has reacted (X — conversion, normally between zero and one), how much of a desired product was formed (Y — yield, normally also between zero and one) and how much desired product was formed in ratio to the undesired product(s) (S ...
The different definitions came from the practice of quoting gravimetric results as mass fractions of the analyte, often expressed as a percentage. A related term was the equivalence factor, one gram divided by equivalent weight, which was the numerical factor by which the mass of precipitate had to be multiplied to obtain the mass of analyte.
centigram: 10 2 g hg hectogram 10 −3 g mg: milligram: 10 3 g kg: kilogram: 10 −6 g μg: microgram (mcg) 10 6 g Mg megagram 10 −9 g ng: nanogram: 10 9 g Gg gigagram 10 −12 g pg picogram 10 12 g Tg teragram 10 −15 g fg femtogram 10 15 g Pg petagram 10 −18 g ag attogram 10 18 g Eg exagram 10 −21 g zg zeptogram 10 21 g Zg zettagram 10 ...
A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and plus (+) and minus (−) signs.
Hecto (symbol: h) is a decimal unit prefix in the metric system denoting a factor of one hundred. It was adopted as a multiplier in 1795, and comes from the Greek แผκατฯν hekatón, meaning "hundred".