Chemistry:2009:CBSE:[Delhi]:Set-III

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  • Q1

    What does the part 6,6 mean in the name nylon 6,6?

    Marks:1
    Answer:

    Nylon 6,6 is obtained by condensation of hexamethylenediamine [(H2N-(CH2)6NH2] and adipic acid  [(HOOC-(CH2)4COOH] under high pressure and high temperature. Both the monomers have 6 carbons each. 6,6 in name of nylon 6,6 indicates the presence of 6 carbon each in adipic acid and hexamethylenediamine.

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  • Q2

    Define the term ‘Tyndall effect’.

    Marks:1
    Answer:

    Tyndall effect is scattering of light by colloidal solutions. When a beam of visible light passes through colloidal solution, it is scattered and the path of beam is illuminated.

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  • Q3

    Why is the froth flotation method selected for the concentration of Sulphide ores ?

    Marks:1
    Answer:

    Sulphide ores are concentrated by froth flotation method because particles of sulphide ore are hydrophobic and they become wet by oil while gangue particles are wetted by water.

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  • Q4

    Give the IUPAC name of the following compound:

     

    Marks:1
    Answer:

    2- bromo 3-methyl but-2 en-1-ol

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  • Q5

    White the structure of 3-oxopentanal.

    Marks:1
    Answer:

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  • Q6

    Why is an alkylamine more basic than ammonia ?

    Marks:1
    Answer:

    Electron donors are bases. Alkyl group is electron donor. Ammonia does not have any alkyl group whereas alkyl amines have alkyl group. Since electron donor groups increase the basicity, alkyl halides are more basic than ammonia.

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  • Q7

    Which is a stronger oxidizing agent Bi(V) or Sb(V)  

    Marks:1
    Answer:

    Bi (V) is stronger oxidizing agent than Sb(V). This is due to the fact that stability of lower oxidation state increases on moving down the group. Under the influence of inert pair effect, Bi(V) has a strong tendency to  convert into Bi(III)
                         Bi(V) + 2 e- ® Bi (III)

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  • Q8

    Which point defect in its crystal units increases the density of a solid?

    Marks:1
    Answer:

    Interstitial defect.

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  • Q9

    A reaction is of second order with respect to a reactant. How will the rate of reaction be affected if the concentration of this reactant is 
    (i)  doubled,
    (ii) reduced to half?

    Marks:2
    Answer:

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  • Q10

    Explain the role of 
    (i)Cryolite in the electrolytic reduction of alumina. 
    (ii)Carbon monoxide in the purification of nickel.

    Marks:2
    Answer:

    (i) Cryolite is added during reduction of alumina to lower its temperature and increase its conductivity. 
    (ii) In purification of nickel, carbon monoxide is added with impure nickel to form volatile nickel tetracarbonyl, which decomposes at high temperature to form pure nickel. 

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