In the Lassaigne's test for nitrogen | Class 11 Chemistry Chapter Organic Chemistry Some Basic Principles and Techniques, Organic Chemistry Some Basic Principles and Techniques NCERT Solutions

Question:

In the Lassaigne's test for nitrogen in an organic compound, the Prussian blue colour is obtained due to the formation of:

(a) Na4[Fe(CN)6]

(b) Fe4[Fe(CN)6]3

(c) Fe2[Fe(CN)6]

(d) Fe3[Fe(CN)6]4

Answer:

In the Lassaigne's test for nitrogen in an organic compound, the sodium fusion extract is boiled with iron (II) sulphate and then acidified with sulphuric acid. In the process, sodium cyanide first reacts with iron (II) sulphate and forms sodium hexacyanoferrate (II). Then, on heating with sulphuric acid, some iron (II) gets oxidised to form iron (III) hexacyanoferrate (II), which is Prussian blue in colour. The chemical equations involved in the reaction can be represented as

Hence, the Prussian blue colour is due to the formation of Fe4[Fe(CN)6]3.


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Welcome to the NCERT Solutions for Class 11 Chemistry - Chapter . This page offers a step-by-step solution to the specific question from Excercise 1 , Question 37: In the Lassaigne's test for nitrogen in an organic compound, the Prussian blue colour is obtaine....