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8.3. Organic chemistry purification and characterization — Chemistry STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceChemistry8.3. Organic chemistry purification and characterization1 Mark
MCQ
The Lassaigne's extract is boiled with conc. $HNO_3$ while testing for halogens. By doing so it
  • ✓
    decomposes $Na_2S$ and $NaCN,$ formed
  • B
    helps in the precipitation of $AgCl$
  • C
    increases the solubility product of $AgCl$
  • D
    increases the concentration of $NO_3^-$ ions
✓

Answer

Correct option: A.
decomposes $Na_2S$ and $NaCN,$ formed
a
$\mathrm{Na}_{2} \mathrm{S}$ and $\mathrm{NaCN},$ if present in the extract, will be

decomposed to $\mathrm{H}_{2} \mathrm{S}$ and $\mathrm{HCN}$ by $HNO_{3}$

$\mathrm{NaCN}+\mathrm{HNO}_{3} \rightarrow \mathrm{NaNO}_{3}+\mathrm{HCN}$

$\mathrm{Na}_{2} \mathrm{S}+2 \mathrm{HNO}_{3} \rightarrow 2 \mathrm{NaNO}_{3}+\mathrm{H}_{2} \mathrm{S}$

These will escape from the solution and will not interfere with the test for halogens.

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