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NEET-XII-Chemistry

Previous Year Paper year:2017

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  • Qstn #1
    The most suitable method of separation of
    1 : 1 mixture of ortho and para-nitrophenols is :
    (1) Steam distillation
    (2) Sublimation
    (3) Chromatography
    (4) Crystallisation
    digAnsr:   1
    Ans : (1)
    Sol. In O-nitrophenol intra molecular H-Bond present. So Bpt is low where as in p-nitrophenol molecules are
    associated by inter molecular H-Bond. So Bpt is high, so o & p-nitrophenol seperated by steam distillation
    method
    O
    H
    δ+
    N = O
    ↓ δ-
    O
    O - nitrophenol
    N
    O
    O ---- H
    O
    H
    NO
    O
    O ---- H
    N O
    O
    O ---- H
    P-nitrophenol
  • Qstn #2
    Which of the following statements is
    not correct?
    (1) Denaturation makes the proteins more active.
    (2) Insulin maintains sugar level in the blood of a human body.
    (3) Ovalbumin is a simple food reserve in egg-white.
    (4) Blood proteins thrombin and fibrinogen are involved in blood clotting.
    digAnsr:   1
    Ans : (1)
    Sol. ∵ Denaturation makes the protein inactive.
    CAREER POINT






  • Qstn #3
    Of the following, which is the product
    formed when cyclohexanone undergoes aldol
    condensation followed by heating?
    (1)
    (2)
    (3)
    (4)
    digAnsr:   3
    Ans : (3)
    Sol.
    O
    O + H
    H
    α
    )OH(-
    onCondensati
    aldol
    /OH
    2
    ⎯⎯ →⎯ Δ
    Θ
    O
  • Qstn #4
    The heating of phenyl-methyl ethers
    with HI produces.
    (1) benzene
    (2) ethyl chlorides
    (3) iodobenzene
    (4) phenol
    digAnsr:   4
    Ans : (4)
    Sol.
    O - CH3 2SN
    HI⎯→⎯
    Methyl Phenyl
    ether
    Phenol
    OH + CH3I
    Methyl iodide
  • Qstn #5
    The correct increasing order of basic
    strength for the following compounds is :



    (1) II < I < III
    (2) II < III < I
    (3) III < I < II
    (4) III < II < I
    digAnsr:   1
    Ans : (1)









    Sol. ∵ Basic strength ∝
    I-,H-,M-
    I,H,M +++
    ∴
    Answer will be : NH2 NH2
    NO2
    NH2
    CH3
    (I) (II)(III)
    〉〉
  • Qstn #6
    Which one of the following pairs of
    species have the same bond order?
    (1) ``N_2``, ``O_2^{-}``
    (2) CO, NO
    (3)`` O_2``, NO
    (4) ``CN^-, CO
    digAnsr:   4
    Ans : (4)
    Sol. CO & CN- are isoelectronic and having same bond order 3
  • Qstn #7
    Name the gas that can readily
    decolourise acidified KMnO4 solution :
    (1) ``P_2O_5 ``
    (2) ``CO_2``
    (3) ``SO_2``
    (4) ``NO_2``
    digAnsr:   3
    Ans : (3)
    Sol. KMnO4 + SO2 + H2SO4 → K2SO4 + MnSO4 + H2O
    ∴ SO2 which is R.A. decolourize KMnO4
  • Qstn #8
    The reason for greater range of oxidation
    states in actinoids is attributed to :
    (1) 4f and 5d levels being close in energies
    (2) the radioactive nature of actinoids
    (3) actinoid contraction
    (4) 5f, 6d and 7s levels having comparable energies
    digAnsr:   4
    Ans : (4)
    Sol. Actinoid shows grater range of oxidation state because 5f, 6d, 7s levels having comparable energies.
  • Qstn #9
    Concentration of the ``Ag^+`` ions in a saturated
    solution of ``Ag_2C_2O_4`` is 2.2 × ``10^{-4}`` mol ``L^{-1}``.
    Solubility product of ``Ag_2C_2O_4`` is :
    (1) 5.3 × ``10^{-12}``
    (2) 2.42 × ``10^{-8}``
    (3) 2.66 × ``10^{-12}``
    (4) 4.5 × ``10^{-11}``
    digAnsr:   1
    Ans : (1)




    Sol. Ag2C2O4
    s2
    Ag2 + +
    s
    OC 2-42
    2s = 2.2 × 10-4
    s = 1.1 × 10-4
    Ksp = 4s3 = 4 × (1.1 × 10-4)3
    = 4 × (1.1)3 × 10-12
    = 5.324 × 10-12 M3
  • Qstn #10
    With respect to the conformers of ethane,
    which of the following statements is true?
    (1) Both bond angles and bond length remains same
    (2) Bond angle remains same but bond length changes
    (3) Bond angle changes but bond length remains same
    (4) Both bond angle and bond length change
    digAnsr:   1
    Ans : (1)
    Sol.
    H
    H H
    H H
    H
    Bond angle ⇒ Unchanged
    Bond length ⇒ Unchanged
    H HH
    H
    H
    H
  • Qstn #11
    Identify A and predict the type of reaction-

    (1)
    (2)
    (3)
    (4)
    digAnsr:   2
    Ans : (2)








    Sol.
    OCH3
    Br
    )NH)(-NaBr(-
    NaNH
    3
    2⎯⎯ →⎯
    H
    OCH3
    ⎯⎯ →⎯ 3HN
    OCH3
    NH3
    Θ
    ⊕
    OCH3
    NH2
    ..
    Intra mol.
    Proton transfer
    Overall Br is replaced by NH2 group so we can say substitution reaction.
  • Qstn #12
    Which of the following is sink for CO?
    (1) Plants
    (2) Haemoglobin
    (3) Micro organisms present in the soil
    (4) Oceans
    digAnsr:   3
    Ans : (3)
    Sol. Soil is a natural sink for carbon monoxide. The soil's ability to remove carbon monoxide from the
    atmosphere is due to the activity of soil micro-organisms.
  • Qstn #13
    In which pair of ions both the species
    contain S - S bond?
    (1) ``S_4O_6^{2-}`` , ``S_2O_7^{2-}``
    (2)``S_2O_7^{2-}`` , ``S_2O_3^{2-}``
    (3)``S_4O_6^{2-}`` , ``S_2O_3^{2-}``
    (4)``S_2O_7^{2-}`` , ``S_2O_8^{2-}``
    digAnsr:   3
    Ans : (3)
    Sol.
    (i)
    O - S - S - S - S - O
    O
    O
    O
    O
    S4O6-2
    O - S - O
    O
    S
    S2O3-2
  • Qstn #14
    Pick out the correct statement with respect to ``[Mn(CN)_6]^{3-}`` :
    (1) It is ``dsp^2`` hybridised and square planar
    (2) It is ``sp^3d^2`` hybridised and octahedral
    (3) It is ``sp^3d^2`` hybridised and tetrahedral
    (4) It is ``d^2sp^3`` hybridised and octahedral
    digAnsr:   4
    Ans : (4)
    Sol. [Mn(CN)6]-3


    25Mn = [Ar] 3d54s2
    Mn+3 = [Ar] 3d4
    CN- is strong ligand
    ∴ Δ0 is high complex is d2sp3 hybridised and inner octahedral
    d2 sp3
    inner octahedral
    n = 2
  • Qstn #15
    The equilibrium constants of the following are :
    ``\ce [N2 +3H2 \rightleftarrows 2NH3``]
    ``\ce [N2 + O2 \rightleftarrows 2NO``]
    ``\ce [H2 + \frac12 O2 \rightleftarrows H2O``]
    The equilibrium constant (K) of the reaction :
    ``\ce 2NH_3 + \frac52 O_2`` ``\xrightleftharpoons{K}`` ``2NO + 3H_2O``
    , will be:
    (1) ``K_2^3`` ``K_3/ K_1``
    (2)``K_1`` ``K_3^3``/``K_2``
    (3) ``K_2`` ``K_3^3``/``K_1``
    (4) ``K_2`` ``K_3``/``K_1``
    digAnsr:   3
    Ans : (3)
    Sol. (1) N2 + 3 H2 2 NH3 K1
    (2) N2 + O2 2 NO K2
    (3) H2 + 2
    1 O2 H2O K3
    Object 2 NH3 + 2
    5 O2
    K 2 NO + 3 H2O
    Equation (3) × 3 + (2) - (1)
    ∴ K =
    1
    3
    32
    K
    KK ×
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