Chemistry:2006

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  • Q1

    A cubic solid is made of two elements X and Y. Atoms Y are at the corners of the cube and X at the body centre. What is the formula of the compound?

    Marks:1
    Answer:

    The contribution due to Y atoms at corner = 1/8
    Number of Y atoms at the corner = 8 x 1/8 = 1
    The contribution due to X atoms at the body centre = 1
    Hence, the
    formula of the compound = XY

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  • Q2

    Two liquids A and B boil at 145°C and 190°C respectively. Which of them has a higher vapour pressure at 80°C?

    Marks:1
    Answer:

    A has higher vapour pressure than B at 800C because boiling point of A is lower than B.

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  • Q3

    For the reaction A B, the rate of reaction becomes twenty seven times when the concentration of A is increased three times. What is the order of the reaction?

    Marks:1
    Answer:

    Rate law expression suggest that,
    rate = k [A]n  
    or, r = k [A]n
    according to question

    27 r = k[3A]n -------------- (ii)

    27 r = 3nk[A]n

    27 r = 3nr                

    27 = 3n

    33 = 3n

    n = 3  
    Hence, order of reaction is 3

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  • Q4

    Write the IUPAC name of: CH3.CH(Br)CH2CONHCH3.

    Marks:1
    Answer:

    3-bromo-N-methylbutanamide

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  • Q5

    Give a chemical test to distinguish between aniline and N-methyl aniline.

    Marks:1
    Answer:

    Aniline gives carbylamine test but N-methyl aniline does not give this test. In this test when aniline is heated with chloroform and alcoholic KOH it forms foul smelling carbylamine.

     

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  • Q6

    What is meant by entropy driven reaction? How can a reaction with positive changes of enthalpy and entropy be made entropy driven?

     out of syllabus

     

    Marks:2
    Answer:

    The reaction where H is positive but -TS is numerically larger then it is known as entropy driven reaction. 
     G = H -TS
    G should be negative for spontaneous reaction.
    The reaction will become entropy driven if
    (i) S is positive and is small but T must be large.
     

    (ii)S is positive and is large but T must be small.

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  • Q7

    Write balanced chemical equations for the following reactions:
    (i)
    Ca3P2 + H2O
    (ii) XeF6 + 3 H2O

    Marks:2
    Answer:

    (i) Ca3P2 + 6H2O 3Ca(OH)2 + 2PH3
    (ii) XeF6 + 3H2O XeO3 + 6HF.

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  • Q8

    Write chemical equations for the reactions involved in the manufacture of potassium permanganate from pyrolusite ore.

    Marks:2
    Answer:

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  • Q9

    What are enantiomers? Draw the structures of the possible enantiomers of 3-methyl pent-1-ene.

    Marks:2
    Answer:

     Those optical isomers which are  non-superimposable mirror image of each other are called enantiomers or enantiomorphs.


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  • Q10

    Write the reactions and the conditions involved in the conversion of:
    a.
    Propene to 1-Propanol (1)
    b.
    Phenol to Salicyclic acid (1)

    Marks:2
    Answer:

    (a) Propene to 1-Propanol:- 

     

    (b) Phenol to Salicylic acid:-

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