Analytical ChemistryHard

Question

The Lassaigne′s extract is boiled with conc HNO3 while testing for halogens. By doing so it

Options

A.helps in the precipitation of AgCl
B.increases the solubility product of AgCl
C.increases the concentration of NO3- ions
D.decomposes Na2S and NaCN, if formed

Solution

Na2S and NaCN, if present in the extract, will be decomposed to H2S and HCN by HNO3 .
NaCN + HNO3 → NaNO3 + HCN
Na2S + 2HNO3 → 2NaNO3 + H2S
These will escape from the solution and will not interfere with the test for halogens.

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