Analytical ChemistryHard
Question
The Lassaigne′s extract is boiled with dil. HNO3 before testing for halogens because
Options
A.Silver halides are soluble in HNO3
B.Na2S and NaCN are decomposed by HNO3
C.Ag2S is soluble in HNO3
D.AgCN is soluble is HNO3
Solution
Na2S and NaCN, formed during fusion with metallic sodium, must be removed before adding AgNO3 otherwise black ppt. due to Na2S or white precipitate due to AgCN will be formed and thus white precipice of AgCl will not identified easily.
Na2S + 2AgNO3 → 2NaNO3 + Ag2S↓
Black
NaCN + AgNO3 → NaNO3 + AgCN ↓
White
NaCl + AgNO3 → NaNO3 + AgCl ↓
White
NaCN + HNO3
NaNO3 + HCN ↑
Na2S + 2HNO3 2NaNO3 + H2S ↑
Na2S + 2AgNO3 → 2NaNO3 + Ag2S↓
Black
NaCN + AgNO3 → NaNO3 + AgCN ↓
White
NaCl + AgNO3 → NaNO3 + AgCl ↓
White
NaCN + HNO3
NaNO3 + HCN ↑ Na2S + 2HNO3
2NaNO3 + H2S ↑ Create a free account to view solution
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