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P Block Elements question

2011 · Q123
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P Block Elements question

2011 · Q123

NEETChemistryP Block ElementsMCQ+4 / −1
The Lassaigne's extract is boiled with conc. HNO3 while testing for halogens. By doing so it
  1. A
    decomposes Na2S and NaCN, formed
  2. B
    helps in the precipitation of AgCl
  3. C
    increases the solubility product of AgCl
  4. D
    increases the concentration of N3−_3^ -3−​ ions
View written solutionFree

Correct answer: A

In case of Lassaigne’s test of halogens, it is necessary to remove NaCN and Na2S from the sodium extract, if nitrogen and sulphur are present. This is done by boiling the sodium extract with conc. HNO3.

NaCN + HNO3 →\to→ NaNO3

  • HCN ↑\uparrow↑

    Na2S + 2HNO3 →\to→ 2NaNO3
  • H2S ↑\uparrow↑
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