Find out the number of cation(s) which form(s) black ppt. (soluble in hot and dilute HNO3) on passing H2S gas into their salt solution? Mg2+(aq.), Cu2+(aq.), Ba2+(aq.), Fe3+(aq.), Ag+(aq.), Al3+(aq.),

Question

Find out the number of cation(s) which form(s) black ppt. (soluble in hot and dilute HNO3) on passing H2S gas into their salt solution? Mg2+(aq.), Cu2+(aq.), Ba2+(aq.), Fe3+(aq.), Ag+(aq.), Al3+(aq.), Hg2+(aq.), Pb2+(aq.), Mn2+(aq.)

Prashant Kotian · Accepted Answer

Correct answer: **3** / CU2+, AG+, AND PB2+ FORM BLACK PRECIPITATES (CUS, AG2S, PBS) WITH H2S WHICH ARE SOLUBLE IN HOT DILUTE HNO3. (NOTE: HG2+ FORMS BLACK HGS BUT IT IS INSOLUBLE IN DIL. HNO3).. Step 1: Identify starting materials: AgCl↓ is a white precipitate (insoluble in water). Step 2: Observe the reaction with cyanide (KCN): CN- is a very strong ligand and coordinates with silver to form a highly stable, soluble complex, [Ag(CN)2]-. Step 3: Since the insoluble precipitate AgCl is dissolved to form a clear soluble complex, this is classified as a precipitate dissolution reaction (type B).

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