Interpretation:
In the qualitative cation analysis for 1.00 mL of the saturated
Concept introduction:
When a solution is treated with HCl and a precipitate is formed, one or more of these cations may be present in the solution; Pb2+, Hg22+, Ag+. To identify these individual cations, the precipitate is filtered and the dried precipitate is further subjected to testing.
PbCl2 is more soluble than other two precipitates; Hg2Cl2 and AgCl. When the temperature increases, solubility of a solid increases. So, when the precipitate obtained from group 1 analysis is washed with hot water, PbCl2 precipitate dissolves in hot water and only Hg2Cl2 and AgCl remains as precipitates. Presence of Pb2+ can be identified by adding a CrO42- solution. When Pb2+ reacts with CrO42-, it forms a yellow color precipitate PbCrO4.
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EBK GENERAL CHEMISTRY
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