高考一轮复习化学离子共存（Review of college entrance examination Chemical Ion coexistence）.doc

高考一轮复习化学离子共存（Review of college entrance examination Chemical Ion coexistence） College entrance examination: a review of chemical ions 1. by double decomposition reaction, not a large number of coexisting ions. (1) gases. Such as CO32-, SO32-, S2-, HCO3-, HSO3-, HS- and H+ are not easily acid volatile acid of coexistence. (2) a precipitate. Such as Ba2+, Ca2+, Mg2+, Ag+ and SO42-, not CO32- a large number of Mg2+, Fe2+ and Ag+ coexist; and Al3+, Zn2+, Cu2+, Fe3+ and OH- cannot coexist; Pb2+ and Cl-, Fe2+ and S2-, Ca2+ and PO43-, Ag+ and I- are not a lot of coexistence. (3) a generation of weak electrolyte. If a large number of OH-, CH3COO-, PO43-, Co HPO42-, H2PO4-, F-, ClO-, AlO2-, SiO32-, CN-, C17H35COO-, and H+ are not some acid; weak acid such as HCO3-, HPO42-, HS-, H2PO4-, HSO3- and OH- cannot coexist; NH4+ and OH- are not a lot of coexistence. (4) some easily hydrolyzed ion in the solution is conditional on the presence of. Such as AlO2-, S2-, CO32- and C6H5O- must be present in the solution under alkaline conditions; such as Fe3+, Al3+ etc. must be under acidic conditions exist in solution. The two types of ions cannot exist at the same time in the same solution, which can double hydrolysis reaction between ions. Such as 3AlO2-+3Al3++6H2O=4Al (OH) 3 case etc.. 2. due to the redox reaction, not a large number of coexisting ions. (1) ions cannot has strong reductive and strong oxidizing ions coexist. Such as S2-, HS-, SO32-, I- and Fe3+ is not a lot of coexistence. (2) due to the oxidation and reduction reaction is not a lot of coexistence in acid or alkaline medium. Such as MnO4-, Cr2O7-, NO3-, ClO- and S2-, HS-, SO32-, HSO3-, I-, Fe2+, SO32- and S2- is not a lot of coexistence; can coexist in alkaline conditions, but under acidic conditions is due to the occurrence of 2S2-+SO32-+6H+=3S +3H2O in response to. H+ and S2O32- are not a lot of coexistence. 3. can hydrolysis with cation anion is not a lot of hydrolysis can coexist in aqueous solution (double hydrolys