Question

Given below are two statements:
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 FeSO4 and Na4[Fe(CN)6].
In the light of the above statements, choose the correct answer from the options given below.

• A. Both Statement I and Statement II are true
• B. Both Statement I and Statement II are false
• C. Statement I is false but Statement II is true
• D. Statement I is true but Statement II is false

Hint:

In Lassaigne's test, the presence of nitrogen and sulfur in an organic compound is tested by forming cyanide and thiocyanate ions after fusion with sodium. Prussian blue formation is specific to compounds containing nitrogen in the form of cyanides.

Answer 1

The Correct Option is D

Lassaigne's test is employed to detect elements such as nitrogen, sulfur, and halogens within organic compounds. The following statements are analyzed in this context.

1. Statement I: "In Lassaigne's test, the covalent organic molecules are transformed into ionic compounds."
   • During Lassaigne's test, organic compounds undergo fusion with sodium metal. This process converts elements covalently bonded in organic molecules, including nitrogen, sulfur, and halogens, into water-soluble sodium salts, which are ionic compounds.
   • For instance, nitrogen is converted into \(NaCN\), sulfur into \(Na_2S\), and halogens into sodium halides like \(NaCl\), \(NaBr\), or \(NaI\).
   • This statement is accurate, as it correctly describes the transformation of covalent bonds into ionic compounds during the test.
2. Statement II: "The sodium fusion extract of an organic compound having N and S gives Prussian blue color with FeSO₄ and Na₄[Fe(CN)₆]."
   • When both nitrogen and sulfur are present in an organic compound, the sodium fusion extract forms sodium thiocyanate, \(NaSCN\).
   • In the presence of HCl, \(NaSCN\) reacts with \(FeSO_4\) to produce a blood-red color, signifying the co-existence of sulfur and nitrogen.
   • A Prussian blue color typically indicates the presence of nitrogen alone, formed when \(FeSO_4\) is reacted with \(Na_4[Fe(CN)_6]\) after oxidation, but this is not the case when both sulfur and nitrogen are present.
   • Consequently, this statement is incorrect because the observed color in the presence of both N and S is blood-red, not Prussian blue.

Based on this analysis, the correct conclusion is: Statement I is true, while Statement II is false.