In the test for halogens,why is nitric acid a | vedclass

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(B) The sodium fusion extract often contains sodium cyanide $(NaCN)$ and sodium sulphide $(Na_2S)$ if nitrogen and sulphur are present in the organic

Vedclass · Accepted Answer

To decompose sodium cyanide and sodium sulphide,which interfere with the test.

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(B) The sodium fusion extract often contains sodium cyanide $(NaCN)$ and sodium sulphide $(Na_2S)$ if nitrogen and sulphur are present in the organic compound. If $AgNO_3$ is added directly,these ions would form precipitates like $AgCN$ and $Ag_2S$,which interfere with the halide test. Adding $HNO_3$ decomposes these species: $NaCN + HNO_3 \rightarrow NaNO_3 + HCN \uparrow$ $Na_2S + 2HNO_3 \rightarrow 2NaNO_3 + H_2S \uparrow$ This ensures that only the halide ions ($Cl^-$,$Br^-$,$I^-$) react with $Ag^+$ to form the characteristic silver halide precipitate.

Column $I$	Column $II$
$A. H_2N-NH_3^+Cl^-$	$p. \text{Sodium fusion extract of the compound gives Prussian blue colour with } FeSO_4$
$B. HO-C_6H_4-CH(NH_3^+)COOH \text{ (with } I^- \text{ counterion)}$	$q. \text{Gives positive } FeCl_3 \text{ test}$
$C. HO-C_6H_4-NH_3^+Cl^-$	$r. \text{Gives white precipitate with } AgNO_3$
$D. (NO_2)_2C_6H_3-NH-NH_3^+Br^-$	$s. \text{Reacts with aldehydes to form the corresponding hydrazone derivative}$

In the test for halogens,why is nitric acid added to the sodium fusion extract before adding silver nitrate?

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