12.37.    In the Lassaigne’s test for nitrogen in an organic compound, the Prussian blue colour is obtained due to the formation of:

               \; (a)\; N\! a_{4}\! \left [ F\! \! \, e(\! C\! N\! )_{6} \right ]                (b)\; F\! e_{4}\left [ F\! e(C\! N)_{6} \right ]_{3}           (c)\; F\! e_{2}\! \left [ F\! e(C\! N)_{6} \right ]           (d) \; F\! e_{3}\left [ F\! e(C\! N)_{6} \right ]_{4}

Answers (1)
M manish

The Prussian blue colour is due to the formation of  Fe_4[Fe(CN)_6]_3.xH_{2}O in Lassaigne's test.

6CN^-+Fe^{2+}\rightarrow [Fe(CN)_6]^{4-}

3[Fe(CN)_6]^{4-}+4Fe^{3+}\rightarrow Fe_4[Fe(CN)_6]_3.xH_{2}O

So, the correct option is (b)

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