Verified Solution • 2025–26 Session moderate

QNEET-2023-Ch-214: NEET 2023 Chemistry - Class 11 NEET-2023-Ch-214 Solution: In Lassaigne's extract of an organic compound both nitrogen and …

In Lassaigne's extract of an organic compound both nitrogen and sulphur are present which gives blood red colour with

Fe^{3+}

due to the formation of- NaSCN

[Fe(CN)_5NOS]^{4-}

[Fe(SCN)]^{2+}

Fe_4[Fe(CN)_6]_3 \cdot xH_2O

Multiple Choice Options

A NaSCN
B $\left[\mathrm{Fe}(\mathrm{CN})_{5} \mathrm{NOS}\right]^{4-}$ [ Fe ( CN ) 5 _ NOS ] 4 _
C $[\mathrm{Fe}(\mathrm{SCN})]^{2+}$ [ Fe ( SCN ) ] 2 +
D $\mathrm{Fe}_{4}\left[\mathrm{Fe}\left(\mathrm{CN}_{6}\right)\right]_{3} \cdot \mathrm{xH}_{2} \mathrm{O}$ Fe 4 _ [ Fe ( CN 6 _ ) ] 3 _ _ xH 2 _ O

Step-by-Step Verified Solution

Sol. In case nitrogen and sulphur both are present in an organic compound, sodium thiocyanate is formed, it give blood red colour and no prussian blue since there are no free cyanide Ions Na + C + N + S _ NaSCN Fe + 3 + SCN _ _ [ Fe ( SCN ) ] 2 + Blood red

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