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ISC Class 12 Chemistry Solved Question Paper 2009

Short Answer Type

31.

How will you bring about the following conversions :

(i) Acetaldehyde to acetamide.

(ii) Phenol to benzoic acid

(iii) Glucose to saccharic acid.

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32. Give the names of the following reactions:

straight i right parenthesis space straight C subscript 2 straight H subscript 5 Br space plus straight C subscript 2 straight H subscript 5 ONa space rightwards arrow straight C subscript 2 straight H subscript 5 OC subscript 2 straight H subscript 5 space plus NaBr ii right parenthesis space CH subscript 3 CHO space plus CH subscript 3 COCH subscript 3 space rightwards arrow with OH to the power of minus on top space CH subscript 3 CH left parenthesis OH right parenthesis CH subscript 2 COCH subscript 3

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33.

How will you distinguish between the following pairs of compounds ? (Give one good chemical test.)

(i) Ethylamine and Acetamide
(ii) Oxalic acid and Acetic acid.

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34. An organic compound A with molecular formula C₂H₇N on reaction with nitrous acid gives a compound B. B on controlled oxidation gives a compound C. C reduces Tollen’s reagent to give silver mirror and D. B reacts with D in the presence of concentrated sulphuric acid to give a sweet smelling compound E. Identify A, B, C, D and E. Give the reaction of C with ammonia and name the product.

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35. Draw the isomers of a compound with the molecular formula C₄H₄O₄. Name the isomers.

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36.

What type of polymerisation takes place when a polyester is formed? Give one example of a polyester and name the monomers from which it is formed.

(ii) Give two examples of natural polymers.

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37.

Identify the products A, B, C and D.

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38.

Give balanced equations for the following reactions:

(i) Formic acid heated with Tollen’s reagent.

(ii) Phenol heated with chloroform and sodium hydroxide.

(iii) Acetaldehyde reacted with phenyl hydrazine.

(iv) Aniline treated with benzoyl chloride.

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Long Answer Type

39.

i) Write the mathematical expression for the first law of thermodynamics.

One mole of an ideal gas is expanded isothermally against a constant pressure of 3 atmospheres from 10 litres to 35 litres. Calculate the work done, change in internal energy and heat absorbed during the process.

(ii) Calculate the free energy change of the reaction:

C_(graphite)+O₂ (g) →CO₂(g) ΔH = - 300 kJ mol^-1 and AS = 3JK^-1 mol^-1 at 300 K.

Predict whether the reaction is spontaneous or not at 300 K.

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40. Describe the extraction of silver from its sulphide ore by the cyanide process.

In the cyanide process the following steps are envolved.

(i) Concentration: The powdered cyanide ore is concentrated by froth flotation process.

(ii) Treatment with sodium cyanide: The concentrate ore is treated with dilute solution of sodium cyanide. A current of air is constantly passed through the solution. After few hours soluble complex of sodium argento cyanide is formed.

Air supplied during the reaction oxidises sodium sulphide to sodium sulphate, so the reaction proceeds in forward direction.

2Na₂S +2O₂ +2H₂O ----> Na₂S₂O₃ +2NaOH
Na₂S₂O₃ +2NaOH 2 O₂ -----> 2Na₂SO₄ +H₂O

(iii) Precipitation of silver : The solution obtained after above step is filtered and treated with scrap zinc to precipitate silver.
2Na[Ag(CN)₂ +Zn -----> Na₂[Zn(CN)₄] +2Ag
sodium tetra cyanozincate

Zinc displaces silver from the complex because it is more electroposetive than silver.

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