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Chemistry : Organic Chemistry – Some Basic Principles and Techniques

Short Answer Type

61. What colour is expected when thiourea is tested for nitrogen by Lassaigne’s method?

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62. A student was given the compound H₂N – C₆H₄ – SO₃H for elemental analysis. While performing Lassaigne’s test for N, what colour will he get and why?

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Multiple Choice Questions

63. In the Lassaigne’s test for nitrogen in an organic compound, the prussian blue colour is obtained due to the formation of:

Na₂[Fe(CN)₆]
Fe₄[Fe(CN)₆]₃
Fe₂[Fe(CN)₆]
Fe₃[Fe(CN)₆]₄

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Short Answer Type

64.

Why Lassaigne's extract is boiled with concentrated HCl while detecting the presence of nitrogen in the compound ?

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65.

Why is it necessary to boil the sodium extract with conc. HNO₃ before testing the halogen?

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66.

Name the method, if any, for the estimation of oxygen in an orangic compound.

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67.

What is the formula of violet coloured compound formed in the Lassaigne's test for sulphur by means of sodium nitroprusside?

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68.

Why a solution of potassium hydroxide is used to absorb carbon dioxide evolved during the estimation of carbon present in an orangic compound?

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69.

Name the methods for the estimation of nitrogen.

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70.

In Kjeldahl's method for estimation of nitrogen, potassium sulphate is also added along with conc. H₂SO₄ for digestion of a compound. Why?

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