BITSAT2020ChemistryGeneral Organic ChemistryActual
The Lassaigne's extract is boiled with dil. HNO ₃ before testing for halogens because
Options
- Asilver halides are soluble in HNO ₃
- BNa ₂ ~S and NaCN are decomposed by HNO ₃
- CAg ₂ ~S is soluble in HNO ₃
- DAgCN is soluble in HNO ₃
Correct answer
B. Na ₂ ~S and NaCN are decomposed by HNO ₃
Step-by-step solution
Na ₂ ~S and NaCN , formed during fusion with metallic sodium, must be removed before adding AgNO ₃, otherwise black ppt. due to Na ₂ ~S or white precipitate due to AgCN will be formed and thus white precipitate of AgCl will not be identified easily. Na ₂ ~S +2 AgNO ₃ 2 NaNO ₃+ Black Ag ₂ ~S NaCN + AgNO ₃ NaNO ₃ + White Ag CN NaCl + AgNO ₃ NaNO ₃+ White Ag Cl Na ₂ ~S +2 HNO ₃ boil 2 NaNO ₃+ H ₂ ~S NaCN + HNO ₃ boil NaNO ₃+ HCN