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Detection of Elements: Lassaigne's Test
Detection of Elements: Lassaigne's Test
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1)
When sodium nitroprusside is added to Lassagne’s extract, a violet colour is formed. It indicates the presence of ______________.
Halogens
Sulphur
Hydrogen
Nitrogen
2)
Which compound does not give a positive result in the Lassaigne’s test for nitrogen?
Urea
Aniline
Benzamide
Glycerine
3)
Which one of the following elements in an organic compound cannot be detected by Lassaigne’s test?
H
Br
N
S
4)
Which one of the following statements is not applicable to Lassaigne’s test?
It can be used for the detection of oxygen in an organic compound.
The elements nitrogen, sulphur and halogens are treated as their inorganic salts.
It is possible to differentiate between chlorine, bromine and iodine.
During fusion, sodium form NaS, NaCN and NaX (X-halogens) with organic compounds.
5)
In the Lassaigne’s test for the detection of nitrogen in an organic compound, the Prussian blue colour is due to the formation of _______________.
K₃[Fe(CN)₆]
Na₄[Fe(CN)₅NOS]
Fe₄[Fe(CN)₆]₃
K₄[Fe(CN)₆]
6)
During the detection of sulphur in an organic compound, the violet colour formed by the addition of sodium nitroprusside to Lassaigne’s extract is due to _____________.
Na₄[Fe(CN)₅NOS]
Na₄[Fe(CN)₅NS]
Na₃[Fe(CN)₅NS]
Na₄[Fe(CN)₅NO]
7)
For the detection of sulphur in an organic compound, Lassaigne’s extract is acidified with acetic acid. Lead acetate solution is then added to it. The black precipitate formed is due to the formation of _______________.
Na₂S
PbS
PbSO₄
PbS₂O₃
8)
Which of the following compounds is formed when an organic compound containing nitrogen is fused with sodium?
NaNO₃
NaNO₂
NaCN
NaNH₂
9)
Which compound is formed when sodium is fused with an organic compound containing iodine?
CHI₃
NaI
CH₃I
NaIO₃
10)
A student added few drops of silver nitrate into Lassaigne’s extract of an organic compound containing bromine. Which one of the following is the correct observation?
A pale yellow precipitate is formed.
A white precipitate is formed.
A black precipitate is formed.
A dark yellow precipitate is formed.