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Analytical Chemistry — Chemistry STD 10 — Question

ICSE BoardEnglish MediumSTD 10ChemistryAnalytical Chemistry3 Marks
Question
In a chemistry lab, a student is given a solution containing an unknown cation. The student adds sodium hydroxide (NaOH) to the solution and observes the formation of a blue precipitate. The student then decides to add ammonium hydroxide to a fresh sample of the solution in excess.
(a) Identify the cation.
(b) What happens when excess of NaOH is added in the solution?
(c) What happens when excess of ammonium hydroxide is added to the solution?
✓

Answer

(a) The cation must be Cu2+.
(b) Deep blue ppt. is insoluble in excess of NaOH.
(c) Pale blue ppt. is soluble in excess of NH4OH.

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