Question
An aqueous solution of a mixture of two inorganic salts, when treated with dilute HCl, gave a precipitate (P) and a filtrate (Q). The precipitate P was found to dissolve in hot water. The filtrate (Q) remained unchanged, when treated with H2S in a dilute mineral acid medium. However, it gave a precipitate (R) with H2S in an ammoniacal medium. The precipitate R gave a coloured solution (S), when treated with H2O2 in an aqueous NaOH medium.
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The coloured solution S contains
⇒ Pb2+ gives ppt. with dil HCl, which is soluble in hot water among Pb2+, Hg22+, Ag+, Hg2+, Pb2+ also give ppt. with dil H+ / H2S.
⇒ Cr3+ does not give ppt with dil. HCl, also does not give ppt. with H+ / H2S but gives coloured ppt. with OH¯ / H2S of green coloured Cr(OH)3, which is soluble in NaOH on reacting with H2O2 gives yellow coloured solution of Na2CrO4.
The precipitate P contains
⇒ Pb2+ gives ppt. with dil HCl, which is soluble in hot water among Pb2+, Hg22+, Ag+, Hg2+, Pb2+ also give ppt. with dil H+ / H2S.
⇒ Cr3+ does not give ppt with dil. HCl, also does not give ppt. with H+ / H2S but gives coloured ppt. with OH¯ / H2S of green coloured Cr(OH)3, which is soluble in NaOH on reacting with H2O2 gives yellow coloured solution of Na2CrO4.