Question:

The Lassaigne's extract is boiled with conc. $HNO_3$ while testing for halogens. By doing so it

Updated On: Jul 13, 2024
  • helps in the precipitation of $AgCl$
  • increases the solubility product of $AgCl$
  • increases the concentration of $NO^-_3$ ions
  • decomposes $Na_2S$ and $NaCN$, if formed
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The Correct Option is D

Solution and Explanation

Na$_2$S and NaCN, if present in the extract, will be
decomposed to H$_2$S and HCN by HNO$_3$ .
NaCN + HN$O_3$ $\rightarrow$ NaN$O_3$ + HCN
Na$_2$S + 2HNO$_3$ $\rightarrow$ 2NaN$O_3$ + H$_2$S
These will escape from the solution and will not
interfere with the test for halogens.
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Top Questions on Methods Of Purification Of Organic Compounds

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Concepts Used:

Purification of Organic Compounds

We commonly use these methods for the purification of substances:

  • Simple crystallization - The most common method that we use to purify organic solids.
  • Fractional crystallization - It is the process of separation of different components of a mixture by repeated crystallisations.
  • Sublimation - Certain organic solids on heating directly change from solid to vapor state without passing through a liquid state. These substances are sublimable. This process is sublimation.
  • Simple distillation - It is the joint process of vaporization and condensation.
  • Fractional distillation - It is the process to separate a mixture of two or more miscible liquids which have boiling points close to each other
  • Distillation under reduced pressure
  • Steam distillation
  • Azeotropic distillation
  • Chromatography