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NEET levelSingle correct optionDifficulty 1 of 3si167

A compound containing both nitrogen and sulphur is fused with a limited amount of sodium. The sodium extract is acidified and treated with $FeCl X_{3}$ . A blood-red colour appears because of

A $[Fe (SCN)] X^{2 +}$
B $Fe X_{4} [Fe (CN) X_{6}] X_{3}$
C $Na X_{4} [Fe (CN) X_{5} NOS]$
D $FeS$

Answer: A

With limited sodium, N and S combine as

NaSCN

. Thiocyanate ions react with

Fe X^{3 +}

to give the blood-red complex

[Fe (SCN)] X^{2 +}

.

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