Question

A solution containing a mixture of metal cations was treated with dilute HCl and no precipitate formed. Next, H2S was bubbled through the acidic solution. A precipitate formed and was filtered off. Then, the pH was raised to about 8 and H2S 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 Bank Felt Ba’t Shot Mn?+ Hgat Agt K* Mg2+ Hg3+ Sn?+ Pb2+ Cd2+ A1+

Answer 1

Soluhon Containing metal Cations is treated with dilute Hal if no precipitate is formed, ie 1st group cations Lead (Pb24), Silver (Ag +) and Mercurous (Hg 24) ions are absent (definetely), when treated with H₂S in presence of acids, I grup Cahors Cu²+, Cd²+, Hgth are precipitated as their Sulphides. There wors in Copper (1), Cadenium (Il & Mercuric com are detinchly present. For the precipitahon of II grup Calons, han de concentration of hulphide lons are enough. In the presence of del. Hal [52] decreases due to Common in effect. Here only I goup Cahom are definently present. When pH as adjusted to 8, the solution becomes basic. In the presence of bases, Sulphide wors Concentrahon intreaks. Hence TV grp Cahorss Ni²t, u ² + Zn 24 are precipitated as their fulphides Detinitely Absent 1 Definitely prent / Possibly preul- p62, Ag + H3, 27 cut? Cd2+ 8634 Mg + Kt Ba2+, Fe +2 A1² Mutz Sn 24 Hg2+