Ncert Solutions Chemistry Class 11th
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12.28. Explain, why an organic liquid vaporises at a temperature below its boiling point in its steam distillation?
12.28. Explain, why an organic liquid vaporises at a temperature below its boiling point in its steam distillation?
It is because in steam distillation the sum of vapour pressure of organic compound and steam should be equal to atmospheric pressure.
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12.27. Name a suitable technique of separation of the components from a mixture of calcium sulphate and camphor.
12.27. Name a suitable technique of separation of the components from a mixture of calcium sulphate and camphor.
Sublimation can be used for the separation of the two compounds because camphor can sublime whereas CaSO4 does not.
Upvote 12.26. Explain the reason for the fusion of an organic compound with metallic sodium for testing nitrogen, sulphur and halogens.
12.26. Explain the reason for the fusion of an organic compound with metallic sodium for testing nitrogen, sulphur and halogens.
Organic compound is fused with sodium metal so as to convert organic compounds into NaCN, Na2S, NaX and Na3PO4. Since these are ionic compounds and become more reactive and thus can be easily tested by suitable reagents.
Upvote 12.25. Why is nitric acid added to sodium extract before adding silver nitrate for testing halogens?
12.25. Why is nitric acid added to sodium extract before adding silver nitrate for testing halogens?
Nitric acid is added to sodium extract so as to decompose NaCN to HCN and Na2S to H2S and to expel these gases.
NaCN + HNO3 ——-> NaNO3 + HCN
Na2S + 2HNO3 ——> 2NaNO3 + H2S
Upvote 12.24. Explain the principle of paper chromatography.
12.24. Explain the principle of paper chromatography.
This is the simplest form of chromatography. Here a strip of paper acts as an adsorbent. It is based on the principle which is partly adsorption. The paper is made of cellulose fibres with molecules of water adsorbed on them. This acts as stationary phase. The mobile phase is the mixture of the comp
Upvote 12.23. Discuss the principle of estimation of halogens, sulphur and phosphorus present in an organic compound.
12.23. Discuss the principle of estimation of halogens, sulphur and phosphorus present in an organic compound.
Estimation of halogens: It involves oxidising the organic substance with fuming nitric acid in the presence of silver nitrate. The halogen of the substance is thus converted to silver halide which is separated and weighed:
Weight of organic compound = W gm
weight of silver halide = x g.
% of halog
Upvote 12.22. Differentiate between the principle of estimation of nitrogen in an organic compound by (i) Dumas method (ii) Kjeldahl’s method.
12.22. Differentiate between the principle of estimation of nitrogen in an organic compound by (i) Dumas method (ii) Kjeldahl’s method.
(i) Dumas method: The nitrogen containing organic compound, when heated with copper oxide in an atmosphere of carbon dioxide, yields free nitrogen in addition to carbon dioxide and water
(ii)Kjeldahl's method: A known mass of the organic compound is heated strongly with conc. H2SO4,
Upvote Lassaigne's test: In organic compounds, nitrogen, sulphur and halogens are covalently bonded. Their detection in 'Lassaigne's test' is possible if they are in the ionic form. This can be achieved by fusing the organic compound with sodium metal.
Chemistry for test for nitrogen:
Sodium fusio
Upvote 12.20. What is the difference between distillation, distillation under reduced pressure and steam distillation? (Intermediate)
12.20. What is the difference between distillation, distillation under reduced pressure and steam distillation? (Intermediate)
Distillation is used in case of volatile liquid mixed with non-volatile impurities.
Distillation under reduced pressure: This method is used to purify such liquids which have very high boiling points and which decompose at or below their boiling points.
Steam distillation is used to purify steam volat
Upvote 12.19. Describe the method, which can be used to separate two compounds with different solubilities in a solvent S.
12.19. Describe the method, which can be used to separate two compounds with different solubilities in a solvent S.
Fractional crystallisation is the method that can be used to separate two compounds with different solubilities in a solvent S. A hot saturated solution of these two compounds is allowed to cool, the less soluble compound crystallises out while the more soluble remains in the solution. The crystals
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