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

Let's analyze the given statements in the context of Lassaigne's test, which is used to detect the presence of elements like nitrogen, sulfur, halogens, etc., in organic compounds. 

1. Statement I: "In Lassaigne's test, the covalent organic molecules are transformed into ionic compounds."
   • In Lassaigne's test, the organic compound is fused with sodium metal. The sodium helps in converting covalently bonded elements like nitrogen, sulfur, and halogens in organic molecules into water-soluble sodium salts (ionic compounds).
   • For example, nitrogen is converted into \(NaCN\), sulfur into \(Na_2S\), and halogens into sodium halides such as \(NaCl\), \(NaBr\), or \(NaI\).
   • This statement is true as it correctly describes the conversion 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]."
   • If both nitrogen and sulfur are present, the sodium fusion extract forms a compound called sodium thiocyanate \(NaSCN\).
   • With FeSO₄ in the presence of HCl, \(NaSCN\) gives a blood-red color, indicating the presence of sulfur and nitrogen together.
   • Prussian blue color is indicative of the presence of nitrogen alone when \(FeSO_4\) is added with Na₄[Fe(CN)₆] (after oxidation), but not when both S and N are present.
   • Hence, this statement is false as the produced color with N and S is blood-red, not Prussian blue.

Therefore, the correct answer is: Statement I is true but Statement II is false.

Answer 2

Statement I: In Lassaigne's test, the covalent organic molecules are transformed into ionic compounds. This statement is true. Lassaigne's test involves fusing the organic compound with sodium metal. The covalent bonds in the compound break down, forming ionic sodium salts, which are soluble in water and can be easily tested for the presence of elements such as nitrogen (N), sulfur (S), and halogens.

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]. This statement is false. The correct reaction that leads to the formation of a prussian blue color indicates the presence of nitrogen alone. When both nitrogen and sulfur are present in the sodium fusion extract, it does not lead to the formation of prussian blue with FeSO4 and Na4[Fe(CN)6]. Instead, it would produce thiocyanate, which does not give a prussian blue color but a red coloration after further reaction with an acidic iron(III) solution.

Conclusion: Statement I is true but Statement II is false.