NEET AIPMT SOLVED PAPER MAINS 2012

  • question_answer
    For real gases van der Waals' equation is. Written as\[\left( p+\frac{a{{n}^{2}}}{{{V}^{2}}} \right)(V-nb)=n\,RT\]written where, a and b are van der Waals' constants.                                                                             Two sets of gases are\[\text{I}\text{.}{{\text{O}}_{\text{2}}}\text{,C}{{\text{O}}_{\text{2}}}\text{,}{{\text{H}}_{\text{2}}}\]and He \[\text{II}\text{.C}{{\text{H}}_{4}}\text{,}{{\text{O}}_{\text{2}}}\]and\[{{\text{H}}_{\text{2}}}\] The gases given in set-I in increasing order of 'b' and gases given in set-II in decreasing order of ' a', are arranged below. Select the correct order from the following,              

    A) \[\text{(I)}\,\text{He}\,\text{}\,{{\text{H}}_{\text{2}}}\text{}\,\text{C}{{\text{O}}_{\text{2}}}\text{}\,{{\text{O}}_{\text{2}}}\] \[\text{(II)}\,\text{C}{{\text{H}}_{\text{4}}}\,\text{}\,{{\text{H}}_{\text{2}}}\text{}\,{{\text{O}}_{\text{2}}}\]

    B) \[\text{(I)}\,\,{{\text{O}}_{\text{2}}}\text{}\,\text{He}\,\,\text{}\,{{\text{H}}_{\text{2}}}\text{}\,\text{C}{{\text{O}}_{\text{2}}}\]\[\text{(II)}\,\,{{\text{H}}_{\text{2}}}\text{}\,{{\text{O}}_{\text{2}}}\,\,\text{}\,\text{C}{{\text{H}}_{4}}\]

    C) \[\text{(I)}\,\,{{\text{H}}_{\text{2}}}\text{}\,\text{He}\,\,\text{}\,{{\text{O}}_{\text{2}}}\text{}\,\text{C}{{\text{O}}_{\text{2}}}\]\[\text{(II)}\,\text{C}{{\text{H}}_{\text{4}}}\text{}\,{{\text{O}}_{\text{2}}}\text{}\,{{\text{H}}_{\text{2}}}\]

    D) \[\text{(I)}\,{{\text{H}}_{2}}<\,{{\text{O}}_{\text{2}}}<\,\text{He}\,\text{}\,\text{C}{{\text{O}}_{\text{2}}}\]\[\text{(II)}\,\,{{\text{O}}_{\text{2}}}\text{}\,\text{C}{{\text{H}}_{\text{2}}}\,\text{}\,{{\text{H}}_{\text{2}}}\]

    Correct Answer: C

    Solution :

    From experimental values of and b, sequence of van der Waals? constant, (b) is                
    Gas \[{{H}_{2}}\] \[He\] \[{{O}_{2}}\] \[C{{O}_{2}}\]
    Value of b \[0.0273\] \[0.0318\] \[0.0273\] \[0.0427\]
    Here correct order is \[{{H}_{2}}<He<{{O}_{2}}<C{{O}_{2}}\] and sequence of van der Waals? constant (a) is                
    Gas \[C{{H}_{4}}\] \[{{O}_{2}}\] \[{{H}_{2}}\]
    Value of b \[2.25\] \[1.36\] \[0.244\]
                                    Hence, correct order is                 \[(II)\,\,C{{H}_{4}}>{{O}_{2}}>{{H}_{2}}\]


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