Question

3.Cold water is added to each of the following pairs of solid salts. In each case state whether a precipitate wil be present, and if so what its composition is. Note: The precipitate may be either one or both of the original salts or one or more of the products formed by reaction between the salts. (10 pts) a. Pb(C2H2O2)2 and NaCl b. BaSO4 and Cus c. Ni(NO3)2 and CaCl2 d. AgCl and Cu(NO3)2 e. Na2CO3 and MgCl2 4. In the analysis of an unknown solution that was known to contain only Group 1 cations (Ag, Pb , Hg2, the white precipitate obtained by adding cold HCl to the unknown solution was completely insoluble in hot water. The residue was completely insoluble in NH3. Indicate which cations are definitely present (+), definitely absent (-), or uncertain (?). (15 pts) - Ag Pb2+ Hg2+ 5. The white precipitate obtained when cold HCl was added to a Group I unknown solution was completely soluble in hot water. Indicate which cations are definitely present (+), definitely absent (-), or uncertain (?). (15 pts) Ag* Pb2+ Hg22+ 6. The white precipitate obtained when cold HCl was added to an unknown solution was completely insoluble in hot water and completely soluble in NH3. Indicate which cations are definitely present (+), definitely absent (-), or uncertain (?). (15 pts) - Ag* Pb2+ 7. The white precipitate obtained when cold HCl was added to a Group I unknown solution was partly soluble in hot water. The residue was partly soluble in NH3. Indicate which cations are definitely present (+), definitely absent (-), or uncertain (?). (15 pts) - Ag* Pb2+ Hg2+

Answer 1

solution (a) Both soluble in in soluble out from lead ace tate and sodium chloride are all cold water. But the product pbcle is in cold watch. Hence, it will precipitate the reaction mixture. pb ( HBO2)₂ + 2 bach - PbCl2 + 2 CH₃COONa. (6) Bason and ans are Hence, both of them insoluble in cold watch. will constitute the precipitate! c) Ni(NO3)2t calle Nicht Ca(NO3)2. Neither the reactants nor the products are in soluble. thence, no precipitate will from. (d, Agel is insoluble in cold water. Cualoza is soluble in wates. Hence, Age will be in the precipitate. (e) lazcoz & Mach MgCO3 + 2NaCl. Nag Co3, MgCl and Nad are soluble in watel, ngcoz is insoluble in cold water. Hence ng coz will precipitate: