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Chemical propertiesBasic oxides 1. Interaction with water. Oxides of alkaline (Li2O, Na2O, K2O, Rb2O, Cs2O) and alkaline-earth (CaO, SrO, BaO) metals form soluble bases - alkalis: Li2O + H2O = 2LiOH; Rb2O + H2O = 2RbOH; CaO + H2O = Ca(OH)2; BaO + H2O = Ba(OH)2. 2. Interaction with acidic oxides forming the salts: K2O + SO2 = K2SO3; SrO + N2O5 = Sr(NO3)2; CuO + SO3 = CuSO4; 3BaO + P2O5 = Ba3(PO4)2. 3. Interaction with acids forming the salts and water: Na2O + 2HNO3 = 2NaNO3 + H2O NiO + H2SO4 = NiSO4 + H2O 3MgO + 2H3PO4 = Mg3(PO4)2 + 3H2O. Other basic oxides do not react with water directly. Acidic oxides 1. The most of acidic oxides reacts with water forming the acids (except a few oxides like SiO2, MoO3, WO3): SO3 + H2O = H2SO4; N2O5 + H2O = 2HNO3; P2O5 + 3H2O = 2H3PO4; 4NO2 + O2 + 2H2O = 4HNO3. 2. Interaction with basic acids with forming the salts: N2O3 + Na2O = 2NaNO2; P2O5 + 3CaO = 2Ca3(PO4)2; SO3 + BaO = BaSO4. 3. Interaction with bases forming the salts and water: SO3 + Ba(OÍ)2 = BaSO4 + H2O; N2O5 + 2ÊOÍ = 2KNO3 + H2O; SiO2+2NaOÍ = Na2SiO3 + H2O.
Amphoteric oxides Term Amphoteric (from Greek) means double-sided, mutual. Therefore amphoteric oxides occupy a position between basic and acidic oxides and display corresponding chemical properties. 1. Interaction with basic and acidic oxides forming the salts: PbO + SO3 = PbSO4; PbO + N2O5 = Pb(NO3)2; Cr2O3 + 3SO3 = Cr2(SO4)3; Cr2O3 + 3N2O5 = 2Cr(NO3)3; Li2O + PbO = Li2PbO2; CaO + PbO = CaPbO2; 3Li2O + Cr2O3 = 2Li3CrO3; Li2O + Cr2O3 = 2LiCrO2; CaO + Cr2O3 = Ca3(CrO3)2; CaO + Cr2O3 = Ca(CrO2)2. 2. Interaction with acids forming the salts and water: PbO+ 2 HCl = PbCl2 + H2O; Al2O3 + 2 H3PO4 = 2AlPO4 + 3H2O. 3. Interaction with alkalis forming the salts and water: Cr2O3 + 6KOH = 2K3CrO3 + 3H2O; MnO2 + 2NaOH = Na2MnO3 + H2O. Peroxides may be shown as a peculiar group of Oxygen-contained compounds. Frequently peroxides are considered as salts of Hydrogen peroxide H2O2, where O2-2 (-O-O-) is an analogue of acid residue. For example, BaO2 - Barium peroxide includes Ba2+ and formally O-. Bases
Bases are complex substances, in which atoms of metals or ionic groups (for example, NH4+) are bonded with one or several hydroxyls groups. Classification of bases: they are divided into two groups - soluble in waters (alkalis - LiOH, NaOH, KOH, RbOH, CsOH, FrOH, Ca(OH)2, Ba(OH)2, Sr(OH)2) and insoluble (for example, Fe(OH)2, Cu(OH)2 etc.). Insoluble bases include amphoteric ones too (Al(OH)3, Cr(OH)3, Zn(OH)2 etc.). According to quantity of OH- bases may be divided into: One-acidic (NaOH); Two-acidic (Ca(OH)2); Three-acidic (Cr(OH)3) and so on.
Preparation 1. Interaction of alkaline and alkaline-earth metals and water forming alkalis and free Hydrogen: 2K + 2H2O = 2KOH + H2; Âà + 2Í2Î = Âà(ÎÍ)2 + Í2; 2. Direct interaction of alkaline and alkaline-earth metals oxides and water forming the alkalis: Na2O + H2O = 2NaOH; CaO + H2O = Ca(OH)2; 3. Insoluble bases may be prepared by interaction between soluble salts of corresponding metals and alkali solution: Cu(NO3)2 + 2LiOH = Cu(OH)2¯ + 2LiNO3; Fe2(SO4)3 + 3Ca(OH)2 = 2Fe(OH)3¯ + 3CaSO4.
Date: 2015-01-12; view: 1702
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