Topic Question Set
Q 1
:
The Lassaigne’s extract is boiled with dilute , before testing for halogens because, [2024]
AgCN is soluble in .
Silver halides are soluble in .
is soluble in .
and NaCN are decomposed by .
(4)
If the salt contains sulphide or cyanide, then Lassaigne’s extract would contain or NaCN. In such cases, upon the addition of in the extract, (black precipitate) or AgCN (white residue) are obtained which interferes with the test for halides. Hence Lassaigne’s extract is boiled with dil. to decompose or NaCN.
Q 2
:
Lassaigne’s test is used for detection of: [2024]
Phosphorous and halogens only
Nitrogen, Sulphur and Phosphorous only
Nitrogen, Sulphur, Phosphorous and halogens
Nitrogen and Sulphur only
(3)
Nitrogen, sulphur, halogens and phosphorus present in an organic compound are detected by “Lassaigne’s test”.
Q 3
:
Which of the following nitrogen containing compound does not give Lassaigne’s test? [2024]
Glycine
Hydrazine
Phenyl hydrazine
Urea
(2)
In Lassaigne's test for nitrogen, NaCN is formed in sodium fusion extract, which is then tested further. Hydrazine () does not contain carbon hence NaCN cannot be formed in sodium fusion extract. So hydrazine does not give Lassaigne 's test for nitrogen.
Q 4
:
Given below are two statements: [2025]
Statement I: Nitrogen, sulphur, halogen and phosphorus present in an organic compound are detected by Lassaigne’s Test.
Statement II: The elements present in the compound are converted from covalent form into ionic form by fusing the compound with Magnesium in Lassaigne’s test.
In the light of the above statements, choose the correct answer from the options given below:
Statement I is false but Statement II is true
Both Statement I and Statement II are false
Both Statement I and Statement II are true
Statement I is true but Statement II is false
(4)
Elements are converted from covalent to ionic form by fusion with sodium metal.
Q 5
:
Given below are two statements: [2025]
Statement I: In Lassaigne’s test, the covalent organic molecules are transformed into ionic compounds.
Statement II: The sodium fusion extract of an organic compound having N and S gives prussian blue colour with and .
In the light of the above statements, choose the correct answer from the options given below:
Statement I is false but Statement II is true
Both Statement I and Statement II are false
Both Statement I and Statement II are true
Statement I is true but Statement II is false
(4)
If an organic compound has both S and N, then its sodium fusion extract gives blood red colour during test of N.
