JEE Main & Advanced Sample Paper JEE Main Sample Paper-8

  • question_answer
    What volume of \[0.2\text{ }M\text{ }RN{{H}_{3}}Cl\]solution should be added to 100 ml. of \[0.1\text{ }M\text{ }RN{{H}_{2}}\]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\[[RN{{H}_{2}}Cl]\]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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