A solution containing a group-IV cation gives a precipitate on passing \(\mathrm{H_2S}\). A solution of this precipitate in dil.HCl produces a white precipitate with NaOH solution and bluish-white precipitate with basic potassium ferrocyanide. The cation is :
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- \(\mathrm{Co^{2+}}\)
- \(\mathrm{Ni^{2+}}\)
- \(\mathrm{Mn^{2+}}\)
- \(\mathrm{Zn^{2+}}\)
The Correct Option is D
Solution and Explanation
\(\mathrm{Zn^{2+} + 2NaOH \rightarrow Zn(OH)_2}\) (white ppt, soluble in excess NaOH).
With potassium ferrocyanide: \(\mathrm{3Zn^{2+} + 2K_4[Fe(CN)_6] \rightarrow K_2Zn_3[Fe(CN)_6]_2}\), a bluish-white precipitate. CoS and NiS are black and do not dissolve in dil. HCl; MnS is buff coloured.
Answer: (4) \(\mathrm{Zn^{2+}}\)
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