Detection of Extra Elements (Nitrogen, Sulphur, Halogens) in Organic Compounds NEET Questions

Organic Chemistry - Principles of Practical Chemistry

Detection of Extra Elements (Nitrogen, Sulphur, Halogens) in Organic Compounds MCQ Questions


13.
During sodium fusion, nitrogen (in an organic compound containing both N and C) is converted to:
A.
Sodium cyanide (NaCN)
B.
Sodium nitrate (NaNO₃)
C.
Ammonium chloride (NH₄Cl)
D.
Sodium amide (NaNH₂)
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ANSWER :
A. Sodium cyanide (NaCN)
14.
In the test for nitrogen, the sodium fusion extract is first boiled with:
A.
Lead acetate
B.
Freshly prepared FeSO₄ solution
C.
AgNO₃ solution
D.
Sodium nitroprusside
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ANSWER :
B. Freshly prepared FeSO₄ solution
15.
Why must FRESHLY prepared FeSO₄ solution be used for the nitrogen test?
A.
Fresh FeSO₄ smells better
B.
Old FeSO₄ becomes radioactive
C.
Old FeSO₄ becomes too acidic
D.
Otherwise FeSO₄ gets oxidised (by air) to ferric sulphate, giving wrong/false results
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ANSWER :
D. Otherwise FeSO₄ gets oxidised (by air) to ferric sulphate, giving wrong/false results
16.
The Prussian blue colour confirming nitrogen is due to formation of:
A.
Ferrous ferricyanide, Fe₃[Fe(CN)₆]₂
B.
Sodium ferrocyanide, Na₄[Fe(CN)₆]
C.
Ferric ferrocyanide, Fe₄[Fe(CN)₆]₃
D.
Iron sulphide, FeS
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ANSWER :
C. Ferric ferrocyanide, Fe₄[Fe(CN)₆]₃
17.
What is added after boiling the extract with FeSO₄ in the nitrogen test?
A.
Acetic acid
B.
Concentrated H₂SO₄ (after cooling)
C.
Concentrated NaOH
D.
Ethanol
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ANSWER :
B. Concentrated H₂SO₄ (after cooling)
18.
The role of concentrated H₂SO₄ (or HCl) in the nitrogen detection test is to:
A.
Dissolve the green Fe(OH)₂ precipitate and oxidise some Fe²⁺ to Fe³⁺
B.
Reduce ferric ions to ferrous ions
C.
Decompose Prussian blue
D.
Neutralise the cyanide ion
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ANSWER :
A. Dissolve the green Fe(OH)₂ precipitate and oxidise some Fe²⁺ to Fe³⁺