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In Lassaigne's test of Sulphur containing compound the appearance of violet colour is due to the presence of 

Option: 1

\mathrm{Na _{4}\left[ Fe ( CN )_{6}\right]}


Option: 2

\mathrm{FeSO _{4}}


Option: 3

\mathrm{\left[F e(C N)_{5} N O S\right]^{4-}}


Option: 4

\mathrm{\left[ Fe ( CN )_{5} N O\right]^{2-}}


Answers (1)

best_answer

As we have learnt,

Test for Sulphur:

In Lassaigne's test of Sulphur containing compound, the violet colour is due to the formation of \mathrm {[ Fe\left ( CN \right )_5NOS ]^{4-}} upon reaction of sodium fusion extract with Nitroprusside anion.

The reaction is given below: 

\mathrm{S}^{2-}+\left[\mathrm { Fe } ( \mathrm { CN } ) _ { 5 } \mathrm { NO }] ^ { 2 - } \longrightarrow \left[\mathrm{Fe}(\mathrm{CN})_{5} \mathrm{NOS}]^{4-}\right.\right.

Hence, the correct answer is Option (3)

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seema garhwal

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