Class 11Chemistry8-3.Organic Chemistry : Purification and characterizationChemical analysis of organic compounds
MediumGive the answers for the Lassaigne test:
$(i)$ If nitrogen and sulphur are both present,what observation is observed?
$(ii)$ If bromine is present,what is the observation?
$(iii)$ In the Lassaigne extract,if black precipitates are not obtained upon adding $CH_3COOH$ and lead acetate,what does this indicate?
$(iv)$ What is the reason for adding $FeSO_4$ to the Lassaigne extract?
$(v)$ Why is the Prussian blue colour observed?
$(vi)$ What does the violet colour with sodium nitroprusside in the Lassaigne extract indicate?
$(i)$ If nitrogen and sulphur are both present,what observation is observed?
$(ii)$ If bromine is present,what is the observation?
$(iii)$ In the Lassaigne extract,if black precipitates are not obtained upon adding $CH_3COOH$ and lead acetate,what does this indicate?
$(iv)$ What is the reason for adding $FeSO_4$ to the Lassaigne extract?
$(v)$ Why is the Prussian blue colour observed?
$(vi)$ What does the violet colour with sodium nitroprusside in the Lassaigne extract indicate?
(N/A) $(i)$ $A$ blood-red colour is obtained due to the formation of $[Fe(SCN)]^{2+}$.
$(ii)$ By adding $AgNO_3$,a pale yellow precipitate of $AgBr$ is formed.
$(iii)$ It indicates that sulphur is absent in the organic compound.
$(iv)$ $FeSO_4$ is added to react with $CN^-$ ions to form ferrocyanide ions,which then react with $Fe^{3+}$ ions.
$(v)$ It is due to the formation of ferric ferrocyanide,$Fe_4[Fe(CN)_6]_3$.
$(vi)$ It indicates that sulphur is present in the compound,forming $Na_4[Fe(CN)_5NOS]$.
$(ii)$ By adding $AgNO_3$,a pale yellow precipitate of $AgBr$ is formed.
$(iii)$ It indicates that sulphur is absent in the organic compound.
$(iv)$ $FeSO_4$ is added to react with $CN^-$ ions to form ferrocyanide ions,which then react with $Fe^{3+}$ ions.
$(v)$ It is due to the formation of ferric ferrocyanide,$Fe_4[Fe(CN)_6]_3$.
$(vi)$ It indicates that sulphur is present in the compound,forming $Na_4[Fe(CN)_5NOS]$.
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