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NEET Sample Paper NEET Sample Test Paper-80

  • question_answer
    A 0.025 m solution of monobasic acid had a freezing point of \[-\,0.060{}^\circ C\]. The \[p{{K}_{a}}\] for the acid is \[({{K}_{b}}\,\,=\,\,1.86\,K-kg\,\,mo{{l}^{-\,1}})\]

    A)  1.2                              

    B)  2

    C)  2.5                              

    D)  5.7

    Correct Answer: C

    Solution :

    Perlon is also known as nylon 6, and nylon 6 is a polymer of caprolactum. \[m=\frac{\Delta {{T}_{b}}}{{{K}_{b}}}=\frac{-\,0.06}{-1.86}\,\,=\,\,3.2\times {{10}^{-\,2}}\,\,=\,\,0.032\] \[\therefore \,\,\,Total particles =\,\,0.032\] Then, number of \[{{\operatorname{H}}^{+}} = \left( 0.032 - 0.025 \right)m =0.007m\] \[{{H}^{+}}/HA\,\,\,{{H}^{+}}+A\] \[[{{H}^{+}}]\,\,=\,\,[{{A}^{-}}]\,\,=\,\,0.007m,\,\,=\,\,HA=0.018\] \[{{K}_{a}}=\frac{{{(0.007)}^{2}}}{0.018}\,\,=\,\,3\times {{10}^{-\,3}}\] \[\operatorname{p}/{{K}_{a}}=\,\,-log\,{{K}_{a}}\,=\,\,-log\,(3\times 1{{0}^{-\,3}})\,=\,\,2.5\]


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