Sodium extract is heated with concentrated H N O 3 before testing for halogens because :

Sodium extract is heated with concentrated

H N O_{3}

before testing for halogens because :

$A g_{2} S$ and AgCN are soluble in acidic medium.
Silver halides are totally insoluble in nitric acid.
$S^{2 -}$ and $C N^{-}$ , if present, are decomposed by conc. $H N O_{3}$ and hence do not interfere in the test.
Ag reacts faster with halides in acidic medium

Solution

S^{2 -}

and

C N^{-}

ions if present are decomposed by conc.

H N O_{3}

and hence do not interfere in the test.

Asked in: JEE Main 2016 (10 Apr Online)

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