Question

Qualitative scheme for seperation of ions Ag, Pb2+, Fe3+, Cu2+, Al3+, Mn2+, Ni2+, Ba

Answer 1

Ag⁺ and Pb²⁺ are group I cations. Cu²⁺ is group II cation. Fe³⁺, Al³⁺, Mn²⁺ and Ni²⁺ are group III cations. Ba²⁺ is group IV cation.

Dilute HCl added to the mixture gives a precipitate contain AgCl(white color) and PbCl₂(white color). Centrifuge the solid and separate out from the solution by filtration. Now PbCl₂ is separated from AgCl by adding Potassium Chromate. The presence of Pb²⁺ can be confirmed by adding a little Potassium Chromate (K₂CrO₄). The Pb²⁺ precipitates as a golden yellow solid characteristic of PbCrO₄^.

To the filtered solution (after centrifugation) add H₂S gas, then Cu²⁺ can be separated from the mixture as CuS. Separate it and again filter the solution.

To the supernatant solution add NH₄Cl solution and NH₃, white color precipitate will form. Wash the precipitate with NH₄NO₃ and centrifuge the solution. Separate the supernatant solution. The precipitate contains Fe³⁺, Al³⁺, Mn²⁺ and Ni²⁺ ions. If the color of the precipitate is blue then it confirms the presence of Fe³⁺, if the precipitate is white gelatinous then it confirms the presence of Al³⁺. Formation of bright pink precipitate confirms the presence of Ni²⁺.

To the supernatant solution add Acetic Acid (CH₃CO₂H) and 1 drop of 1M K₂CrO₄. A yellow precipitate indicates the presence of Ba²⁺.