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JEE Main & Advanced Sample Paper JEE Main Sample Paper-11

  • question_answer
    What volume of 0.2 M \[RN{{H}_{3}}Cl\]solution should be added to 100 ml. of 0.1 M \[RN{{H}_{2}}\] solution to produce a buffer solution of pH = 8.7? Given: \[p{{K}_{b}}\] of \[RN{{H}_{2}}=5,\], log 2 = 0.3

    A)  50 ml.                  

    B)  100 ml.

    C)  200 ml.                

    D)  None of these

    Correct Answer: B

    Solution :

     Let V ml of \[RN{{H}_{3}}Cl\]added into \[RN{{H}_{2}}\]solution \[[RN{{H}_{3}}Cl]\]in resultant solution \[=\frac{0.2\times V}{100+V}\] \[[RN{{H}_{2}}]=\frac{100\times 0.1}{100+V};pOH=p{{K}_{b}}+\log \frac{[RNH_{3}^{+}]}{[RN{{H}_{2}}]}\] \[5.3=5+\log \left[ \frac{\left( \frac{0.2\times V}{100+V} \right)}{\frac{100\times 0.1}{100+V}} \right]\] \[\therefore \] \[2=\frac{0.2\times V}{10}\Rightarrow V=100ml.\]


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