Q1: Why is Cu2+ placed in Group IIB and Ni2+ in Group IIIB in qualitative inorganic analysis?
Explanation: Cu2+ forms CuS in acidic medium, while Ni2+ precipitates only in basic medium.
Q2: What reagent is used to precipitate Group IIB cations like Cu2+?
Explanation: H₂S in acidic medium causes precipitation of Cu2+ as CuS.
Q3: Why does Cu2+ form a deep blue complex with NH₃ while Ni2+ forms a pale violet one?
Explanation: Cu2+ forms tetraammine complex (deep blue); Ni2+ forms hexaammine (pale violet).
Q4: Which reagent gives a red precipitate with Ni2+ but not with Cu2+?
Explanation: DMG gives a red ppt with Ni2+ — a classic confirmatory test.
Q5: What happens when H₂S is passed through acidic solution of Cu2+ and Ni2+?
Explanation: Only Cu2+ precipitates in acidic medium. Ni2+ needs ammoniacal medium.
Q6: What is the color of CuS formed in acidic medium?
Explanation: CuS is black in color.
Q7: What reagent helps in separating Ni2+ from Cu2+ after dissolution in HNO₃?
Explanation: NH₄OH forms complexes with both ions and enables further differentiation.
Q8: What is the oxidation state of copper in [Cu(NH₃)₄]2+?
Explanation: Cu remains in +2 oxidation state in this complex.
Q9: Which is the most confirmatory test for Ni2+?
Explanation: Red precipitate with DMG confirms Ni2+.
Q10: In which medium does Ni2+ precipitate as NiS?
Explanation: Ni2+ forms NiS in ammoniacal medium, not in acidic.
Q11: Which reagent gives a pink precipitate with Mn2+ in ammoniacal solution?
Explanation: H₂S gives MnS as a pink solid in basic medium.
Q12: What happens when Zn2+ is treated with excess NaOH?
Explanation: Zn(OH)₂ is amphoteric and dissolves in excess NaOH forming [Zn(OH)₄]2-.
Q13: What is the confirmatory test for Mn2+ in basic medium?
Explanation: In basic medium, Mn2+ oxidizes to MnO₂, forming a brown precipitate.
Q14: What is the color of the precipitate formed when Zn2+ is treated with H₂S in ammoniacal medium?
Explanation: Zn2+ forms ZnS, which is white in color, in ammoniacal medium.
Q15: Which reagent is used to confirm the presence of Co2+ by forming a deep blue complex?
Explanation: NH₄SCN forms a blue complex in presence of acetone with Co2+, confirming its presence.
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