Question

A solution containing a mixture of metal cations was treated with dilute HCl and no precipitate formed. Next, H, S was bubbled through the acidic solution. A precipitate formed and was filtered off. Then, the pH was raised to about 8 and HS was again bubbled through the solution. A precipitate again formed and was filtered off. Finally, the solution was treated with a sodium carbonate solution, which resulted in no precipitation Classify the metal ions based on whether they were definitely present, definitely absent, or whether it is possible they were present in the original mixture. Definitely present Definitely absent Possibly present

Answer 1

Group I cations are lead, silver and mercuric ions. These are precipitated as their chlorides when treated with HCl.

pot (Leadcon), Hez (Mercurous on), Agt (Silver wors) are definetly absent. Copper (Capsic) cuctions, Sn²+ (Stannous) +) 36 37 are definetly Meraisc (4 ), (Antimary) present Bart, Kt, Mg²+ erat Nizt mut2 may be present. p62, Ag+ & Hg 2 Cahors are called 1st group cations. These are precipitated as their chlorides. Since no precipitate is formed when treated with Hy, definetly we ces day that it smp cations are Absent. cut suht Hot, sbts are called and grap. Cations. There are precipitated as their Gelphides. When solutions Containing metal ions is treated with He followed by H₂S, forms a black recepitate. Along with there 4 coin, may e ph27 ako present. The phre, which is not Precipitated in this group. Hence may be prefent.

Since no precipitate is formed on treatment with Dil.HCl, 1st group cations are absent. Then through the resultant solution, Hydrogen sulphide gas is passed. If a black precipitate is formed, 2nd group cations (cupric ions, Stannous ions, mercuric ions and Antimony (III) ions ) are present. H2S gas passed for 3-4 times until all the ions completely precipitated. Then solution is filtered and filtrate is treated for group 3 cations.

Cations definitely absent are : Lead Pb(II) ion, silver Ag(I) ion and mercuric Hg(I) ion.

Cations definitely present are copper ions, Stannous ions, mercuric ions and Antimony III ions.