Qualitative Analysis - Result Question 30

####30. Which of the following statement(s) is (are) correct with reference to the ferrous and ferric ions?

(1998,2M)

(a) Fe3+ gives brown colour with potassium ferricyanide

(b) Fe2+ gives blue precipitate with potassium ferricyanide

(c) Fe3+ gives red colour with potassium thiocyanate

(d) Fe2+ gives brown colour with ammonium thiocyanate

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Answer:

Correct Answer: 30. (c)

Solution:

  1. The blue precipitate of Fe2+ ion with potassium ferricyanide is due to formation of Turnbull’s blue KFe[Fe(CN)6].

Fe2++K3[Fe(CN)6]KFe[Fe(CN)6]+2K+

The red colour of Fe3+ ion with potassium thiocyanate is due to formation of [Fe(SCN)3].

Fe3++3KSCN[Fe(SCN)3]+3K+ Red coloured 



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