JEE Main202430 Jan 2024Morning ShiftChemistryPractical ChemistryActual
The Lassiagne's extract is boiled with dil HNO 3 before testing for halogens because,
Options
- AAgCN is soluble in HNO 3
- BSilver halides are soluble in HNO 3
- CAg 2 S is soluble in HNO 3
- DNa 2 S and NaCN are decomposed by HNO 3
Correct answer
D. Na 2 S and NaCN are decomposed by HNO 3
Step-by-step solution
The Lassaigne’s extract is first boiled with dil. HNO 3 to decompose cyanide or sulphide of sodium (NaCN or Na 2 S) formed during Lassaigne’s test. These ions would otherwise interfere with silver nitrate test for halogen. NaCN ( aq ) + HNO 3 ( aq ) → NaNO 3 ( aq ) + HCN ( ↑ ) Na 2 S ( aq ) + 2 HNO 3 ( aq ) → 2 NaNO 3 ( aq ) + H 2 S ( ↑ ) Hence option D is the answer.