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WBJEE 2016 Solved Physics & Chemistry Question Paper–Part 5

Jan 19, 2017 18:27 IST

    WBJEE is a common entrance examinations held at state level for admission to the Undergraduate Level Engineering and Medical courses in the State of West Bengal.  Find WBJEE Solved Physics & Chemistry Question Paper 2016 for undergraduate level engineering exam. Previous year question papers help aspirants in understanding exam pattern, question format, important topics and assessing preparation. It has also been seen that sometimes questions are repeated in WBJEE Exam. Detailed solution of each question has been provided so that students do not lose their precious time in searching solutions of these questions.

    The Physics and Chemistry section of WBJEE Paper has 80 multiple choice questions. Out of 80 questions 40 questions are of Chemistry and rest 40 questions are of Physics.

    41. The condition for a reaction to occur spontaneously is
    (A) ΔH must be negative
    (B) ΔS  must be negative
    (C) (ΔH-TΔS) must be negative
    (D) (ΔH+TΔS) must be negative

    Ans : (C)

    Sol.

    When ΔG<0 then the reaction occur spontaneously.
    Also, ΔG= ΔH-TΔS
    So, for spontaneous reaction ΔH-TΔS should be negative.

    42. The order of equivalent conductances at infinite dilution of LiCl, NaCl and KCl is
    (A) LiCl>NaCl>KCl
    (B) KCl>NaCl>LiCl
    (C) NaCl>KCl>LiCl
    (D) LiCl>KCl>NaCl

    Ans : (B)

    Sol.
    K+ ion is larger than Na+ ion so the distance between the K+ and Cl- ions is greater than that between Na+ and Cl-, decreasing bond strength. So, NaCl has high bond energy than KCl.
    So, the order of equivalent conductance is:
    KCl>NaCl>LiCl

    43. The molar solubility (in mol L–1) of a sparingly soluble salt MX4 is ‘S’. The corresponding solubility product is ‘Ksp’. ‘S’ in terms of’Ksp’ is given by the relation
    (A)  S=(Ksp/128)(1⁄4)
    (B) S=(Ksp/256)(1⁄5)
    (C) S=(256/Ksp)(1⁄5)
    (D) S=(128/Ksp)(1⁄4)

    Ans : (B)

    Sol.

    WBJEE

    Ksp=[M(+4) ]×[X- ]4=S×(4S)4=256S5
    &there4;S=(KSP/256)(1⁄5)

    44. Ozonolysis of an alkene produces only one dicarbonyl compound. The structure of the alkene is :
    (A) H3 C—CH=CH—CH3

    WBJEE

    (D)

    CH3—CH=CH—CH=CH2

    Ans : (B)

    Sol.

    WBJEE

    Sequence and Series: Practice Questions Set 1

    45. From the following compounds choose the one which is not aromatic :

    WBJEE

    Ans : (B)

    Sol.

    WBJEE

    this compound is cyclo octa tetraene which is non polar. Hence this is non aromatic compound.

    46. Amongst the following compounds, the one that will not respond to Cannizzaro reaction upon treatment with alkali is

    (A)  Cl3CCHO

    (B) Me3CCHO

    (C) C6H5CHO

    (D) HCHO

    Ans : (A)

    Sol.

    Cl3CCHO formation is the 2nd last step in the haloform reaction mechanism. Hence on treatment  with caustic alkali, Cl3CCHO is hydrolysed and does not disproportionate.

    WBJEE

    47. Which of the following compounds would not react with Lucas reagent at room temperature?

    (A)  H2C=CHCH2OH

    (B) C6H5CH2OH

    (C)  CH3CH2CH2OH

    (D) (CH3)3COH

    Ans : (C)

    Sol.

    Lucas' reagent is a solution of anhydrous zinc chloride in concentrated hydrochloric acid. The reaction is a substitution in which the chloride replaces a hydroxyl group. Since, CH 3CH2 CH 2OH does not undergo SN1 or SN2 at room temperature so, this compound will not react with Lucas reagent at room temperature.

    48. Amongst the following compounds the one which would not respond to iodoform test is

    (A)  CH3CH(OH)CH2CH3

    (B) ICH2COCH2CH3

    (C)  CH3COOH

    (D) CH3CHO

    Ans : (C)

    Sol.

    The reaction of iodine and base with methyl ketones is so reliable that the "iodoform test" (the appearance of a yellow precipitate) is used to probe the presence of a methyl ketone. In acetic acid, the most acidic proton is attached to O atom. So deprotonation of α– hydrogen does not occur and hence no haloform reaction.

    49. Which of the following will be dehydrated most readily in alkaline medium?

    WBJEE

    Ans : (B)

    Sol.

    WBJEE

    So, the correct option is B.

    50. The correct order of basicity of the following compounds is

    WBJEE

    (A) 1 < 2 < 3 < 4

    (B) 1 < 2 < 4 < 3

    (C)  2 < 1 < 3 < 4

    (D) 4 < 3 < 2 < 1

    Ans : (C)

    Sol.

    WBJEE

    So, the correct order of basicity is 2 < 1 < 3 < 4

    Sequence and Series: Practice Questions Set 1

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