The Lassaigne's extract is boiled with conc HNO_3 while testing for halogens. By doing so it

Correct answer: D. decomposes Na_2 ~S and NaCN , if formed Na_2 ~S and NaCN, if present in the extract, will be decomposed to H_2 ~S and HCN by HNO_3 . aligned & NaCN+HNO_ 3 NaNO_ 3 +HCN & Na_ 2 ~S+2 HNO_ 3 2 NaNO_ 3 + H_ 2 ~S aligned These will escape from the solution and will not interfere with the test for halogens.

NEET 2011

Exam: NEET
Year: 2011
Subject: Chemistry
Chapter: General Organic Chemistry

NEET 2011 · Chemistry · General Organic Chemistry

The Lassaigne's extract is boiled with conc HNO_3 while testing for...

The Lassaigne's extract is boiled with conc

\mathrm{HNO}_3

while testing for halogens. By doing so it

Options

Ahelps in the precipitation of $\mathrm{AgCl}$
Bincreases the solubility product of $\mathrm{AgCl}$
Cincreases the concentration of $\mathrm{NO}_3^{-}$ ions
Ddecomposes $\mathrm{Na}_2 \mathrm{~S}$ and $\mathrm{NaCN}$ , if formed

Correct answer

D. decomposes $\mathrm{Na}_2 \mathrm{~S}$ and $\mathrm{NaCN}$ , if formed

Step-by-step solution

\mathrm{Na}_2 \mathrm{~S}

and NaCN, if present in the extract, will be decomposed to

\mathrm{H}_2 \mathrm{~S} and \mathrm{HCN}

\mathrm{HNO}_3

\begin{aligned}& \mathrm{NaCN}+\mathrm{HNO}_{3} \longrightarrow \mathrm{NaNO}_{3}+\mathrm{HCN}\\ & \mathrm{Na}_{2} \mathrm{~S}+2 \mathrm{HNO}_{3} \longrightarrow 2 \mathrm{NaNO}_{3}+ \mathrm{H}_{2} \mathrm{~S} \end{aligned}

These will escape from the solution and will not interfere with the test for halogens.

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