Molecular mass is a dimensionless quantity numerically equal to the molar mass. Molecular mass (older name molecular weight) is the mass of a molecule calculated as the sum of the mass of each atom in the molecule multiplied by the number of atoms of that element in the molecule. However, chemists almost always express molar masses in g/mol for convenience. In SI, the unit for molar mass is kg/mol. In other words, it is the mass of one mole of a particular substance. The molar mass is a physical property, which is defined as the mass of a substance divided by its amount of substance in moles. One mole of pure carbon-12 has a mass of exactly 12 grams. The mole as the unit of measurement for the amount of substance is one of the seven base units of the International System of Units (SI). In other words, the mole is the amount of substance equal in mass to the combined mass in atomic mass units of the atoms of molecules of the substance multiplied by the Avogadro constant or Avogadro number. An elementary entity may be an atom, a molecule, an ion, an electron, any other particle or specified group of particles.Īvogadro constant N A = 6.02214076×10²³ mol⁻¹ The amount of substance, symbol n, of a system is a measure of the number of specified elementary entities. This number is the fixed numerical value of the Avogadro constant, N A, when expressed in the unit mol⁻¹ and is called the Avogadro number. One mole contains exactly 6.02214076×10²³ elementary entities. The mole, symbol mol, is the SI unit of the amount of substance. The mole is used to express the amounts of reactants and products of chemical reactions. In chemistry, it is important to measure their amounts accurately. Roselite is an arsenate that contains cobalt, magnesium and calcium and forms red crystals.All substances consist of atoms or molecules. Magnesium, iron and manganese form the phosphate mineral ludlamite. Magnesium appears with aluminum and iron in the phosphate lazulite. Magnesium appears with fluorine in the silicate Norbergite.Magnesium phosphate forms the mineral Newberyite. Magnesium appears with manganese and arsenic in the silicate Ardennite. ![]() Magnesium with calcium forms the gem mineral diopside which has the composition CaMgSi 2O 6. The mineral forsterite, Mg 2SiO 4, is used for green gems. Magnesium silicate of composition MgSiO 3 occurs in the mineral form enstatite which is sometimes of gem quality. As the ingredient of baby powders and other talcum products, it certainly has a more benign image than those magnesium silicates which make up asbestos. Another silicate of magnesium is talc, Mg 3Si 3O 10(OH) 3. Another fibrous magnesium silicate without iron is chrysotile. Those minerals include tremolite, riebeckite and grunerite. Magnesium, along with iron, is a constituent of the fibrous silicate minerals which were collectively given the commercial name asbestos. Magnesium appears with zinc and arsenic in the silicate mcgovernite. Magnesium appears in the carbonate mineral Benstonite. Magnesium forms the hydroxide Mg(OH) 2 which in mineral form is called Brucite. It forms an oxide along with manganese and other metals in the mineral birnessite. With aluminum it forms the oxide mineral spinel. Another oxide with boron (borate) with iron and titanium is warwickite. The compound with boron is called boracite. It appears with chromium in the carbonate mineral stichtite. It appears with copper in the carbonate mineral Callaghanite. Magnesium is found with boron in the oxide minerals inderite and kurnakovite. ![]() It appears with boron in the fibrous mineral Szaibelyite. It appears with iron in the carbonate pyroaurite and in the mineral Hulsite. Magnesium is contained in the carbonate minerals dolomite, CaMg(CO 3) 3, magnesite MgCO 3 and artenite Mg 2CO 3(OH) 2.3H 2O. Magnesium is the final member of the big 8 elements in the Earth's crust, being the eighth most abundant element at about 2.1% by weight. Magnesium is a key component in chlorophyll, the molecule in green plants which helps transform sunlight and carbon dioxide into water and sugar. Magnesium sulfate, MgSO 4.7H 2O is called Epsom salt and is used as a cleansing agent. Magnesium oxide, MgO is called magnesia and is used medically for neutralizing excess stomach acid and as a laxative ("milk of magnesia" is MgO in water). Magnesium powder and an oxidizing agent is used as flash powder. The metal burns in air with a bright white light, leading to application in flares. Magnesium reacts with boiling water to form magnesium hydroxide and hydrogen gas. This low density is used to advantage in alloys like magnalium (10% magnesium, 90% aluminum). Only calcium and the alkali metals are lighter.
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