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Home » Three students, Manish, Ramesh and Rajni were determining the extra elements present in an organic compound given by their teacher. They prepared the Lassaigne’s extract (L.E.) independently by the fusion of the compound with sodium metal. Then they added solid FeSO4 and dilute sulphuric acid to a part of Lassaigne’s extract. Manish and Rajni obtained Prussian blue colour but Ramesh got a red colour. Ramesh repeated the test with the same Lassaigne’s extract but again got red colour only. They were surprised and went to their teacher and told him about their observation. A teacher asked them to think over the reason for this. Can you help them by giving the reason for this observation? Also, write the chemical equations to explain the formation of compounds of different colours
Three students, Manish, Ramesh and Rajni were determining the extra elements present in an organic compound given by their teacher. They prepared the Lassaigne’s extract (L.E.) independently by the fusion of the compound with sodium metal. Then they added solid FeSO4 and dilute sulphuric acid to a part of Lassaigne’s extract. Manish and Rajni obtained Prussian blue colour but Ramesh got a red colour. Ramesh repeated the test with the same Lassaigne’s extract but again got red colour only. They were surprised and went to their teacher and told him about their observation. A teacher asked them to think over the reason for this. Can you help them by giving the reason for this observation? Also, write the chemical equations to explain the formation of compounds of different colours
CBSE | Chemistry | Class 11 | Exercise 1 | ncert exemplar | Organic Chemistry – Some Basic Principles & Techniques
Three students, Manish, Ramesh and Rajni were determining the extra elements present in an organic compound given by their teacher. They prepared the Lassaigne’s extract (L.E.) independently by the fusion of the compound with sodium metal. Then they added solid FeSO4 and dilute sulphuric acid to a part of Lassaigne’s extract. Manish and Rajni obtained Prussian blue colour but Ramesh got a red colour. Ramesh repeated the test with the same Lassaigne’s extract but again got red colour only. They were surprised and went to their teacher and told him about their observation. A teacher asked them to think over the reason for this. Can you help them by giving the reason for this observation? Also, write the chemical equations to explain the formation of compounds of different colours

3NaCNS + FeSO4 + dilute sulphuric→ Fe(CNS)3 (Blood red colour) + 3Na+

Ramesh’s organic molecule has both Nitrogen and Sulphur, resulting in the Blood-red colour of Fe(CNS)3, whereas Manish and Rajni’s organic compound contains just Nitrogen, resulting in the Prussian blue colour.

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