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Board Paper of Class 12-Science 2011 Chemistry Delhi(SET 3) - Solutions

General Instructions:
(i) All questions are compulsory
(ii) Question numbers 1 to 8 are very short-answer questions and carry 1 mark each.
(iii) Question numbers 9 to 18 are short-answer questions and carry 2 marks each.
(iv) Question numbers 19 to 27 are also short-answer questions and carry 3 marks.
(v) Question numbers 28 to 30 are long-answer questions and carry 5 marks each.
(vi) Use Log Tables, if necessary. Use of calculators is not allowed.
  • Question 1

    ‘Crystalline solids are anisotropic in nature’. What does this statement mean?

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  • Question 2

    Express the relation among the conductivity of solution in the cell, the cell constant and the resistance of solution in the cell.

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  • Question 3

    Define ‘shape-selective catalysis’.

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  • Question 5

    Arrange the following compounds in an increasing order of their solubility in water: 

    C6H5NH2, (C2H5)2NH, C2H5NH2

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  • Question 6

    Write the IUPAC name of the following compound: 

    (CH3)3 CCH2Br

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  • Question 7

    Draw the structure of 3-methylbutanal.

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  • Question 8

    In nylon 6, 6 what does the designation ‘6, 6’ mean?

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  • Question 9

    What type of a battery is lead storage battery? Write the anode and the cathode reactions and the overall reactions occurring in a lead storage battery.

     

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  • Question 10

    Two half-reactions of an electrochemical cell are given below:

    Construct the redox equation from the standard potential of the cell and predict it the reaction is reactant favoured or product favoured.

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  • Question 11

    State reasons for each of the following: 

    (i) The N − O bond in is shorter than the N − O bond in

    (ii) SF6 is kinetically an inert substance. 

    OR

    State reasons for each of the following: 

    (i) All the P-Cl bonds in PCl5 molecule are not equivalent. 

    (ii) Sulphur has greater tendency for catenation than oxygen.

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  • Question 12

    Distinguish between ‘rate expression’ and ‘rate constant’ of a reaction.

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  • Question 13

    Assign reasons for each of the following: 

    (i) Transition metals generally form coloured compounds. 

    (ii) Manganese exhibits the highest oxidation state of +7 among the 3d series of transition elements. 

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  • Question 14

    How would you obtain 

    (i) Picric acid (2, 4, 6-trinitrophenol) from phenol, 

    (ii) 2-Methylpropene from 2-methylpropanol? 

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  • Question 15

    Explain the following giving one example for each: 

    (i) Reimer-Tiemann reaction. 

    (ii) Friedel Craft’s acetylation of anisole.

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  • Question 16

    Describe what you understand by primary structure and secondary structure of proteins.

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  • Question 17

    What is essentially the difference between α-form of glucose and β-form of glucose? Explain.

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  • Question 18

    Name the sub-groups into which polymers are classified on the basis of magnitude of intermolecular forces.

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  • Question 19

    The density of lead is 11.35 g cm−3 and the metal crystallizes with fcc unit cell. Estimate the radius of lead atom (At. Mass of lead = 207 g mol−1 and NA = 6.02 × 1023 mol−1

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  • Question 20

    Explain how the phenomenon of adsorption finds application in each of the following processes:

    (i) Production of vacuum

    (ii) Heterogeneous catalysis

    (iii) Froth Floatation process

    OR

    Define each of the following terms:

    (i) Micelles

    (ii) Peptization

    (iii) Desorption

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  • Question 21

    Nitrogen pentoxide decomposes according to equation: 2N2O5(g) → 4NO2(g) + O2(g) 

    This first order reaction was allowed to proceed at 40° C and the data below were collected:

    [N2O5] (M) Time (min)
    0.400 0.00
    0.289 20.0
    0.209 40.0
    0.151 60.0
    0.109 80.0

    (a) Calculate the rate constant. Include units with your answer. 

    (b) What will be the concentration of N2O5 after 100 minutes? 

    (c) Calculate the initial rate of reaction.

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  • Question 22

    Complete the following chemical equations:

    (i)

    (ii)

    (iii)

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  • Question 23

    Write the name, stereochemistry and magnetic behaviour of the following: 

    (At. nos. Mn = 25, Co = 27, Ni = 28) 

    (i) K4[Mn(CN)6

    (ii) [Co(NH3)5Cl]Cl2

    (iii) K2[Ni(CN)4]

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  • Question 24

    Describe the principle behind each of the following processes:

    (i) Vapour phase refining of a metal.

    (ii) Electrolytic refining of a metal.

    (iii) Recovery of silver after silver ore was leached with NaCN.

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  • Question 25

    Answer the following: 

    (i) Haloalkanes easily dissolve in organic solvents, why? 

    (ii) What is known as a racemic mixture? Give an example. 

    (iii) Of the two bromoderivatives, C6H5CH(CH3)Br and C6H5CH(C6H5)Br, which one is more reactive in substitution reaction and why? 

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  • Question 26

    Complete the following chemical equations: 

    (i)

    (ii) C6H5N2Cl + H3PO2 + H2O →

    (iii) 

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  • Question 27

    Answer the following questions: 

    (i) Why do soaps not work in hard water? 

    (ii) What are the main constituents of dettol? 

    (iii) How do antiseptics differ from disinfectants?

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  • Question 28

    (a) Give chemical tests to distinguish between 

    (i) Propanal and propanone, 

    (ii) Benzaldehyde and acetophenone. 

    (b) How would you obtain 

    (i) But-2-enal from ethanal, 

    (ii) Butanoic acid from butanol, 

    (iii) Benzoic acid from ethylbenzene? 

    OR

    (a) Describe the following giving linked chemical equations: 

    (i) Cannizzaro reaction 

    (ii) Decarboxylation 

    (b) Complete the following chemical equations: 

    (i) 

    (ii) 

    (iii)

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  • Question 29

    (a) Explain the following: 

    (i) NF3 is an exothermic compound whereas NCl3 is not. 

    (ii) F2 is most reactive of all the four common halogens. 

    (b) Complete the following chemical equations: 

    (i) C + H2SO4 (conc) →

    (ii) P4 + NaOH + H2O →

    (iii)

    OR

    (a) Account for the following: 

    (i) The acidic strength decreases in the order HCl > H2S > PH3

    (ii) Tendency to form pentahalides decreases down the group in group 15 of the periodic table. 

    (b) Complete the following chemical equations: 

    (i) P4 + SO2Cl2

    (ii) XeF2 + H2O →

    (iii)

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  • Question 30

    (a) Differentiate between molarity and molality for a solution. How does a change in temperature influence their values? 

    (b) Calculate the freezing point of an aqueous solution containing 10.50 g of MgBr2 in 200 g of water. (Molar mass of MgBr2 = 184 g) (Kf for water = 1.86 K kg mol−1

    OR

    (a) Define the terms osmosis and osmotic pressure. Is the osmotic pressure of a solution a colligative property? Explain. 

    (b) Calculate the boiling point of a solution prepared by adding 15.00 g of NaCl to 250.0 g of water. (Kb for water = 0.512 K kg mol−1), (Molar mass of NaCl = 58.44 g)

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