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Why is pb2+ kept in both groups 1 and 2?
Why is Pb2+ kept in both groups 1 and 2? ................
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Dinesh khalmaniya 1
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Lead has been placed in group 1st and 2nd because lead chloride is slightly soluble in water and therefore, lead is never completely precipitated by adding dilute HCl to a sample; the rest of the lead ions are precipitated with H2S in acidic medium.
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In the 1st group lead is expected to get precipitated as lead(II) chloride. But, PbCl2 has significant solubility in water, and its solubility increases in the presence of excess Cl- ions due to the formation of the complex, [PbCl4]2-. Still, when dil.HCl is added to a solution of a soluble lead salt like lead nitrate, a part of the metal ions gets precipitated as lead(II) chloride. Pb(2+) + 2Cl(-) = PbCl2(s) The metal ions remaining in solution are precipitated as insoluble lead sulphide on passing H2S into the filtrate (in the 2nd group). Pb(2+) + H2S(g) = PbS(s) + 2H(+) Since lead is not completely precipitated by HCl in the 1st group, it is placed in both the group
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Priyanshu kumar Best Answer
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Lead has been placed in group 1st and 2nd because lead chloride is slightly soluble in water and therefore, lead is never completely precipitated by adding dilute HCl to a sample; the rest of the lead ions are precipitated with H2S in acidic medium