The main direct effect of sulfates on the climate involves the scattering of light, effectively increasing the Earth's albedo. They increase the acidity of the atmosphere and form acid rain. Sulfates occur as microscopic particles ( aerosols) resulting from fossil fuel and biomass combustion. Alum, a double sulfate with the formula K 2Al 2(SO 4) 4♲4H 2O, figured in the development of the chemical industry. Green vitriol is ferrous sulfate heptahydrate, FeSO 4♷H 2O blue vitriol is copper sulfate pentahydrate, CuSO 4♵H 2O and white vitriol is zinc sulfate heptahydrate, ZnSO 4♷H 2O. The vitriol salts, from the latin vitreolum, glassy, were so-called because they were some of the first transparent crystals known. The sulfate ion is used as counter ion for some cationic drugs.Gypsum, the natural mineral form of hydrated calcium sulfate, is used to produce plaster.Magnesium sulfate, commonly known as Epsom salts, is used in therapeutic baths.Some anaerobic microorganisms, such as those living near deep sea thermal vents use sulfates as electron acceptors.The lead-acid battery typically uses sulfuric acid.Sulfates are important in both the chemical industry and biological systems: The Pauling bonding representation for sulfate and other main group compounds with oxygen is a common way of representing the bonding in many textbooks. This explanation is quoted in some current textbooks. In this description, while there is some π character to the S-O bonds, the bond has significant ionic character. A widely accepted description involves pπ - dπ bonding, initially proposed by D.W.J Cruickshank, where fully occupied p orbitals on oxygen overlap with empty sulfur d orbitals (principally the d z 2 and d x 2- y 2). The outcome was a broad consensus that d orbitals play a role, but are not as significant as Pauling had believed. Pauling's use of d orbitals provoked a debate on the relative importance of π bonding and bond polarity (electrostatic attraction) in causing the shortening of the S-O bond. The double bonding was taken by Pauling to account for the shortness of the S-O bond (149 pm). His reasoning was that the charge on sulfur was thus reduced, in accordance with his principle of electroneutrality. Later, Linus Pauling used valence bond theory to propose that the most significant resonance canonicals had two π bonds (see above) involving d orbitals. no double bonds and a formal charge of 2+ on the sulfur atom. The first description of the bonding in modern terms was by Gilbert Lewis in his groundbreaking paper of 1916 where he described the bonding in terms of electron octets around each atom, i.e. The tetrahedral geometry of the sulfate ion is as predicted by VSEPR theory. The S-O bond length of 149 pm is shorter than expected for a S-O single bond for example the bond lengths in sulfuric acid are 157 pm for S-OH. The metal-oxygen bonds in sulfate complexes can have significant covalent character. An example is the neutral metal complex PtSO 4P(C 6H 5) 3 2 where the sulfate ion is acting as a bidentate ligand. The sulfate ion can act as a ligand attaching either by one oxygen (monodentate) or by two oxygens as either a chelate or a bridge. The appearance of a white precipitate, which is barium sulfate, indicates that sulfate anions are present. The barium derivative is useful in the gravimetric analysis of sulfate: one adds a solution of, perhaps, barium chloride to a solution containing sulfate ions. Exceptions include calcium sulfate, strontium sulfate, and barium sulfate, which are poorly soluble. Many examples of ionic sulfates are known, and many of these are highly soluble in water. reacting sulfuric acid with a metal hydroxide or oxide.Methods of preparing ionic sulfates include: Organic sulfates, such as dimethyl sulfate, are covalent compounds and esters of sulfuric acid. The sulfate ion carries a negative two charge and is the conjugate base of the bisulfate (or hydrogen sulfate) ion, HSO 4 −, which is the conjugate base of H 2SO 4, sulfuric acid. The sulfate ion is a polyatomic anion with the empirical formula S O 4 2− and a molecular mass of 96.06 daltons it consists of a central sulfur atom surrounded by four equivalent oxygen atoms in a tetrahedral arrangement.
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