![]() The hydrated derivative, CrCl 2(H 2O) 4, forms monoclinic crystals with the P2 1/c space group. Ball-and-stick model of chromium(II) chloride tetrahydrate. The Cr centres are octahedral, being distorted by the Jahn-Teller Effect. It crystallizes in the Pnnm space group, which is an orthorhombically distorted variant of the rutile structure making it isostructural to calcium chloride. Cr + n H 2O + 2 HCl → CrCl 2(H 2O) n + H 2 Structure and properties Īnhydrous CrCl 2 is white however commercial samples are often grey or green. Treatment of chromium powder with concentrated hydrochloric acid gives a blue hydrated chromium(II) chloride, which can be converted to a related acetonitrile complex. ![]() On the laboratory scale, LiAlH 4, zinc, and related reductants produce chromous chloride from chromium(III) precursors:Ĥ CrCl 3 + LiAlH 4 → 4 CrCl 2 + LiCl + AlCl 3 + 2 H 2 2 CrCl 3 + Zn → 2 CrCl 2 + ZnCl 2ĬrCl 2 can also be prepared by treating a solution of chromium(II) acetate with hydrogen chloride: Cr 2(OAc) 4 + 4 HCl → 2 CrCl 2 + 4 AcOH ![]() Chromium(II) chloride has no commercial uses but is used on a laboratory-scale for the synthesis of other chromium complexes.ĬrCl 2 is produced by reducing chromium(III) chloride either with hydrogen at 500 ☌: The anhydrous solid is white when pure, however commercial samples are often grey or green it is hygroscopic and readily dissolves in water to give bright blue air-sensitive solutions of the tetrahydrate Cr(H 2O) 4Cl 2. These relative weights computed from the chemical equation are sometimes called equation weights.Chromium(II) chloride describes inorganic compounds with the formula Cr Cl 2(H 2O) n. For bulk stoichiometric calculations, we are usually determining molar mass, which may also be called standard atomic weight or average atomic mass.įormula weights are especially useful in determining the relative weights of reagents and products in a chemical reaction. This is not the same as molecular mass, which is the mass of a single molecule of well-defined isotopes. This is how to calculate molar mass (average molecular weight), which is based on isotropically weighted averages. The atomic weights used on this site come from NIST, the National Institute of Standards and Technology. The percentage by weight of any atom or group of atoms in a compound can be computed by dividing the total weight of the atom (or group of atoms) in the formula by the formula weight and multiplying by 100. If the formula used in calculating molar mass is the molecular formula, the formula weight computed is the molecular weight. The formula weight is simply the weight in atomic mass units of all the atoms in a given formula. When calculating molecular weight of a chemical compound, it tells us how many grams are in one mole of that substance. Using the chemical formula of the compound and the periodic table of elements, we can add up the atomic weights and calculate molecular weight of the substance.įinding molar mass starts with units of grams per mole (g/mol). This site explains how to find molar mass. The reason is that the molar mass of the substance affects the conversion. To complete this calculation, you have to know what substance you are trying to convert. In chemistry, the formula weight is a quantity computed by multiplying the atomic weight (in atomic mass units) of each element in a chemical formula by the number of atoms of that element present in the formula, then adding all of these products together.Ī common request on this site is to convert grams to moles.
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