JEE Main · 2022 · 25 Jun 2022 · Shift 2 · Practical and Analytical Chemistry

During halogen test, sodium fusion extract is boiled with concentrated

HNO_{3}

(A)remove unreacted sodium
(B)decompose cyanide or sulphide of sodium✓ Correct
(C)extract halogen from organic compound
(D)maintain the pH of extract

Answer: (B)

Solution

In the Lassaigne's test for halogens, the sodium fusion extract is boiled with concentrated

HNO_{3}

to decompose sodium cyanide (

NaCN

) and sodium sulphide (

Na X_{2} S

) that may be present. These compounds would interfere with the halogen test by forming precipitates with silver nitrate. The nitric acid oxidizes and removes these interfering species, ensuring that any precipitate formed with

AgNO X_{3}

is due to halide ions only.

JEE Main · 2022 · 25 Jun 2022 · Shift 2 · Single correct option

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