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34-997: MCH may refer to: Biology and medicine [ edit ] Mean corpuscular hemoglobin or mean cell hemoglobin Maternal and child health Melanin concentrating hormone Molecular clock hypothesis Microfibrillar collagen hemostat Master of Surgery , written as either M.Ch. or Ch.M. People and entities [ edit ] Michael C. Hall , actor New Zealand's Ministry for Culture and Heritage Places [ edit ] Ehime Prefectural Matsuyama Central Senior High School , Matsuyama, Ehime, Japan Machala , Ecuador (IATA airport code MCH) March railway station , England (National Rail station code MCH) MCH Arena , football stadium in Herning, Denmark, home to FC Midtjylland Mitcham railway station, Melbourne , station code MCH Municipal Corporation of Hyderabad ,

68-454: A century earlier. In chemistry, it has been known since Proust's law of definite proportions (1794) that knowledge of the mass of each of the components in a chemical system is not sufficient to define the system. Amount of substance can be described as mass divided by Proust's "definite proportions", and contains information that is missing from the measurement of mass alone. As demonstrated by Dalton's law of partial pressures (1803),

102-450: A fact that greatly aided their acceptance: It was not necessary for a chemist to subscribe to atomic theory (an unproven hypothesis at the time) to make practical use of the tables. This would lead to some confusion between atomic masses (promoted by proponents of atomic theory) and equivalent weights (promoted by its opponents and which sometimes differed from relative atomic masses by an integer factor), which would last throughout much of

136-414: A mass of exactly 12  g . The four different definitions were equivalent to within 1%. Because a dalton , a unit commonly used to measure atomic mass , is exactly 1/12 of the mass of a carbon-12 atom, this definition of the mole entailed that the mass of one mole of a compound or element in grams was numerically equal to the average mass of one molecule or atom of the substance in daltons, and that

170-449: A measurement of mass is not even necessary to measure the amount of substance (although in practice it is usual). There are many physical relationships between amount of substance and other physical quantities, the most notable one being the ideal gas law (where the relationship was first demonstrated in 1857). The term "mole" was first used in a textbook describing these colligative properties . Developments in mass spectrometry led to

204-553: A mole is the Avogadro number (symbol N 0 ) and the numerical value of the Avogadro constant (symbol N A ) expressed in mol . The value was chosen on the basis of the historical definition of the mole as the amount of substance that corresponds to the number of atoms in 12  grams of C , which made the mass of a mole of a compound expressed in grams, numerically equal to the average molecular mass or formula mass of

238-555: A solution is commonly expressed by its molar concentration , defined as the amount of dissolved substance per unit volume of solution, for which the unit typically used is mole per litre (mol/L). The number of entities (symbol N ) in a one-mole sample equals the Avogadro number (symbol N 0 ), a dimensionless quantity . Historically, N 0 approximates the number of nucleons ( protons or neutrons ) in one gram of ordinary matter . The Avogadro constant (symbol N A = N 0 /mol ) has numerical multiplier given by

272-448: A special name derived from the mole is the katal , defined as one mole per second of catalytic activity . Like other SI units, the mole can also be modified by adding a metric prefix that multiplies it by a power of 10 : One femtomole is exactly 602,214,076 molecules; attomole and smaller quantities cannot be exactly realized. The yoctomole, equal to around 0.6 of an individual molecule, did make appearances in scientific journals in

306-486: A substance is equal to its relative atomic (or molecular) mass multiplied by the molar mass constant , which is almost exactly 1 g/mol. Like chemists, chemical engineers use the unit mole extensively, but different unit multiples may be more suitable for industrial use. For example, the SI unit for volume is the cubic metre, a much larger unit than the commonly used litre in the chemical laboratory. When amount of substance

340-521: A substance was redefined as containing "exactly 6.022 140 76 × 10 elementary entities" of that substance. Since its adoption into the International System of Units in 1971, numerous criticisms of the concept of the mole as a unit like the metre or the second have arisen: October 23, denoted 10/23 in the US, is recognized by some as Mole Day . It is an informal holiday in honor of

374-427: Is a unit of measurement , the base unit in the International System of Units (SI) for amount of substance , a quantity proportional to the number of elementary entities of a substance. One mole contains exactly 6.022 140 76 × 10 elementary entities (approximately 602 sextillion or 602 billion times a trillion), which can be atoms, molecules, ions, ion pairs, or other particles . The number of particles in

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408-438: Is also expressed in kmol (1000 mol) in industrial-scaled processes, the numerical value of molarity remains the same, as kmol m 3 = 1000  mol 1000  L = mol L {\textstyle {\frac {\text{kmol}}{{\text{m}}^{3}}}={\frac {1000{\text{ mol}}}{1000{\text{ L}}}}={\frac {\text{mol}}{\text{L}}}} . Chemical engineers once used

442-461: Is calculated by dividing the total mass of hemoglobin by the number of red blood cells in a volume of blood. MCH=(Hb*10)/RBC (in millions) A normal MCH value in humans is 27 to 33 picograms (pg)/cell. The amount of hemoglobin per RBC depends on hemoglobin synthesis and the size of the RBC. The mass of the red cell is determined by the iron (as part of the hemoglobin molecule), thus MCH in picograms

476-470: Is roughly the mass of one red cell. In iron deficiency anemia the cell mass becomes lighter, thus a MCH below 27 pg is an indication of iron deficiency. The MCH decreases when Hb synthesis is reduced, or when RBCs are smaller than normal, such as in cases of iron-deficiency anemia. Conversion to SI-units: 1 pg of hemoglobin = 0.06207 femtomole (fmol). Normal value converted to SI-units : 1.68 – 1.92 fmol/cell. Femtomole The mole (symbol mol )

510-484: The 2019 revision of the SI , which redefined the mole by fixing the value of the Avogadro constant, making it very nearly equivalent to but no longer exactly equal to the gram-mole), but whose name and symbol adopt the SI convention for standard multiples of metric units – thus, kmol means 1000 mol. This is equivalent to the use of kg instead of g. The use of kmol is not only for "magnitude convenience" but also makes

544-414: The kilogram-mole (notation kg-mol ), which is defined as the number of entities in 12 kg of C, and often referred to the mole as the gram-mole (notation g-mol ), then defined as the number of entities in 12 g of C, when dealing with laboratory data. Late 20th-century chemical engineering practice came to use the kilomole (kmol), which was numerically identical to the kilogram-mole (until

578-480: The 14th CGPM. Before the 2019 revision of the SI , the mole was defined as the amount of substance of a system that contains as many elementary entities as there are atoms in 12 grams of carbon-12 (the most common isotope of carbon ). The term gram-molecule was formerly used to mean one mole of molecules, and gram-atom for one mole of atoms. For example, 1 mole of MgBr 2 is 1 gram-molecule of MgBr 2 but 3 gram-atoms of MgBr 2 . In 2011,

612-872: The 24th meeting of the General Conference on Weights and Measures (CGPM) agreed to a plan for a possible revision of the SI base unit definitions at an undetermined date. On 16 November 2018, after a meeting of scientists from more than 60 countries at the CGPM in Versailles, France, all SI base units were defined in terms of physical constants. This meant that each SI unit, including the mole, would not be defined in terms of any physical objects but rather they would be defined by physical constants that are, in their nature, exact. Such changes officially came into effect on 20 May 2019. Following such changes, "one mole" of

646-527: The Avogadro number with the unit reciprocal mole (mol ). The ratio n = N / N A is a measure of the amount of substance (with the unit mole). Depending on the nature of the substance, an elementary entity may be an atom , a molecule , an ion , an ion pair, or a subatomic particle such as a proton . For example, 10 moles of water (a chemical compound ) and 10 moles of mercury (a chemical element ) contain equal numbers of substance, with one atom of mercury for each molecule of water, despite

680-420: The adoption of oxygen-16 as the standard substance, in lieu of natural oxygen. The oxygen-16 definition was replaced with one based on carbon-12 during the 1960s. The International Bureau of Weights and Measures defined the mole as "the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilograms of carbon-12." Thus, by that definition, one mole of pure C had

714-400: The basic SI unit of mol/s were to be used, which would otherwise require the molar mass to be converted to kg/mol. For convenience in avoiding conversions in the imperial (or US customary units ), some engineers adopted the pound-mole (notation lb-mol or lbmol ), which is defined as the number of entities in 12 lb of C. One lb-mol is equal to 453.592 37  g‑mol , which is

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748-488: The chemical convenience of having oxygen as the primary atomic mass standard became ever more evident with advances in analytical chemistry and the need for ever more accurate atomic mass determinations. The name mole is an 1897 translation of the German unit Mol , coined by the chemist Wilhelm Ostwald in 1894 from the German word Molekül ( molecule ). The related concept of equivalent mass had been in use at least

782-578: The compound expressed in daltons . With the 2019 revision of the SI , the numerical equivalence is now only approximate but may be assumed for all practical purposes. The mole is widely used in chemistry as a convenient way to express amounts of reactants and amounts of products of chemical reactions . For example, the chemical equation 2 H 2 + O 2 → 2 H 2 O can be interpreted to mean that for each 2 mol molecular hydrogen (H 2 ) and 1 mol molecular oxygen (O 2 ) that react, 2 mol of water (H 2 O) form. The concentration of

816-422: The definition of the gram was not mathematically tied to that of the dalton, the number of molecules per mole N A (the Avogadro constant) had to be determined experimentally. The experimental value adopted by CODATA in 2010 is N A = 6.022 141 29 (27) × 10  mol . In 2011 the measurement was refined to 6.022 140 78 (18) × 10  mol . The mole was made the seventh SI base unit in 1971 by

850-484: The equations used for modelling chemical engineering systems coherent . For example, the conversion of a flowrate of kg/s to kmol/s only requires dividing by the molar mass in g/mol (as kg kmol = 1000  g 1000  mol = g mol {\textstyle {\frac {\text{kg}}{\text{kmol}}}={\frac {1000{\text{ g}}}{1000{\text{ mol}}}}={\frac {\text{g}}{\text{mol}}}} ) without multiplying by 1000 unless

884-613: The nineteenth century. Jöns Jacob Berzelius (1779–1848) was instrumental in the determination of relative atomic masses to ever-increasing accuracy. He was also the first chemist to use oxygen as the standard to which other masses were referred. Oxygen is a useful standard, as, unlike hydrogen, it forms compounds with most other elements, especially metals . However, he chose to fix the atomic mass of oxygen as 100, which did not catch on. Charles Frédéric Gerhardt (1816–56), Henri Victor Regnault (1810–78) and Stanislao Cannizzaro (1826–1910) expanded on Berzelius' works, resolving many of

918-434: The number of daltons in a gram was equal to the number of elementary entities in a mole. Because the mass of a nucleon (i.e. a proton or neutron ) is approximately 1 dalton and the nucleons in an atom's nucleus make up the overwhelming majority of its mass, this definition also entailed that the mass of one mole of a substance was roughly equivalent to the number of nucleons in one atom or molecule of that substance. Since

952-605: The predecessor to Greater Hyderabad Municipal Corporation Other uses [ edit ] Memory Controller Hub , another name for the northbridge or host bridge, which is a microchip on some PC motherboards MicroTCA Carrier Hub , a component of the MicroTCA embedded computing standard The month of March, in British National Rail abbreviations Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with

986-480: The problems of unknown stoichiometry of compounds, and the use of atomic masses attracted a large consensus by the time of the Karlsruhe Congress (1860). The convention had reverted to defining the atomic mass of hydrogen as 1, although at the level of precision of measurements at that time – relative uncertainties of around 1% – this was numerically equivalent to the later standard of oxygen = 16. However

1020-416: The same numerical value as the number of grams in an international avoirdupois pound . Greenhouse and growth chamber lighting for plants is sometimes expressed in micromoles per square metre per second, where 1 mol photons ≈ 6.02 × 10 photons. The obsolete unit einstein is variously defined as the energy in one mole of photons and also as simply one mole of photons. The only SI derived unit with

1054-435: The solid is composed of a certain number of moles of such entities. In yet other cases, such as diamond , where the entire crystal is essentially a single molecule, the mole is still used to express the number of atoms bound together, rather than a count of molecules. Thus, common chemical conventions apply to the definition of the constituent entities of a substance, in other cases exact definitions may be specified. The mass of

MCH - Misplaced Pages Continue

1088-501: The title MCH . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=MCH&oldid=1223781691 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Mean corpuscular hemoglobin It

1122-489: The two quantities having different volumes and different masses. The mole corresponds to a given count of entities. Usually, the entities counted are chemically identical and individually distinct. For example, a solution may contain a certain number of dissolved molecules that are more or less independent of each other. However, the constituent entities in a solid are fixed and bound in a lattice arrangement, yet they may be separable without losing their chemical identity. Thus,

1156-459: The year the yocto- prefix was officially implemented. The history of the mole is intertwined with that of units of molecular mass , and the Avogadro constant . The first table of standard atomic weight was published by John Dalton (1766–1844) in 1805, based on a system in which the relative atomic mass of hydrogen was defined as 1. These relative atomic masses were based on the stoichiometric proportions of chemical reaction and compounds,

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