JEE Main & Advanced Sample Paper JEE Main Sample Paper-20

  • question_answer
    What volume of \[0.2\,M\,RN{{H}_{3}}Cl\] solution should be added to \[100ml\]. of \[0.1\,RN{{H}_{2}}\]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 \[=\frac{0.2\times V}{100+V}\] \[[RN{{H}_{2}}]=\frac{100\times 0.1}{100+V};pOH=p{{K}_{b}}+\log \frac{[RNH_{3}^{+}]}{[RN{{H}_{2}}]}\] \[5.3=5+\log \left[ \frac{\left( \frac{0.2\times V}{100+V} \right)}{\frac{100\times 0.1}{100+V}} \right]\]\[\therefore \] \[2=\frac{0.2\times V}{10}\Rightarrow V=V=100ml.\]


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