Chemistry:2005:CBSE:[All India]

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  • Q1

    How many atoms can be assigned to its unit cell if an element forms (i) body centered cubic cell, and (ii) a face centered cubic cell?

    Marks:1
    Answer:

    Number of atoms present in a


    (i) Body centred cubic cell = 11/8 + 1= 2


    (ii) Face centred cubic cell = 11/6 + 1= 4

           

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  • Q2

    What would be the value of Van't Hoff factor for a dilute solution of K2SO4 in water?

    Marks:1
    Answer:

    3

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  • Q3

    Express the relation between the half-life period of a reactant and its initial concentration for a reaction of nth order.

    Marks:1
    Answer:

       

     Where n is the order of reaction.

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  • Q4

    Mention a chemical property in which methanoic acid differs from acetic acid.

    Marks:1
    Answer:

     Methanoic acid reduces tollen’s reagent where as acetic acid does not reduce tollen’s reagent.

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  • Q5

    How is the basic strength of aromatic amines affected by the presence of an electron releasing group on the benzene ring?

    Marks:1
    Answer:

     When an electron releasing group is present in an aromatic amine ring especially on ortho and para position will stabilize the ammonium cation formed on protonation of amine and hence increases the basic strength of an aromatic amine.

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  • Q6

    Show that the uncertainty principle is of little significance for an object of mass 10-3 g

    Marks:2
    Answer:

     This question is not in syllabus of 2007-2008.

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  • Q7

    Write chemical equations for the following reactions:

    (i) Ca3(PO4)2 + SiO2 + C

    (ii) XeF6 +H2O

    Marks:2
    Answer:

    (i) 2Ca3(PO4)2 + 6SiO2 + 10C  P4 + 6CaSiO3 + 10CO

    (ii) XeF6 + 3H2O  XeO3 + 6HF

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  • Q8

    Predict the products of electrolysis obtained at the electrodes in each case when the electrodes used are of platinum:
    (i) An aqueous solution of AgNO3.
    (ii) An aqueous solution of H2SO4.

    Marks:2
    Answer:

    (i) When an aqueous solution of AgNO3 is electrolyzed using platinum electrodes, decomposition of silver would take place on inert cathode and the evolution of oxygen would take place at the anode. 

     

    (ii)When an aqueous solution of sulphuric acid (H2SO4) is electrolyzed using platinum electrodes the evolution of hydrogen gas at the cathode and evolution of gas at the anode would occur.

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  • Q9

    How are polymers classified on the basis of forces operating between their molecules? To which, of these classes does nylon-66 belong?

    Marks:2
    Answer:

    On the basis of forces operating between their molecules polymers are classified into four classes. These are given below:-
    (i)Elastomers:- In this type of polymers chains are held together by the weakest intermolecular forces. e.g., Vulcanized rubber.
    (ii) Fibers:- In this of polymers monomers are held together by strong intermolecular forces like hydrogen bonding. e.g., nylon 66.
    (iii)Thermoplastics:- In this type of polymers interaction forces in between molecules are intermediate between elastomers and fibers.e.g., polyethylene, polystyrene.
    (iv)Thermosetting:- In this type of polymers, monomers are cross-link together by three dimensional network of bonds. e.g., bakelite.

     

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  • Q10

    State that de Broglie relationship. How do de Broglie waves of a moving particle differ from electromagnetic waves?  out of syllabus

    Marks:2
    Answer:

     This question is not in syllabus of 2007-2008.

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