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JEE Main & Advanced Chemistry Equilibrium / साम्यावस्था Question Bank Critical Thinking

  • question_answer
    Calculate the amount of \[{{(N{{H}_{4}})}_{2}}S{{O}_{4}}\] in grams which must be added to 500 ml of \[0.200\,M\,N{{H}_{3}}\] to yield a solution with \[pH=9.35\] \[({{K}_{b}}\] for \[N{{H}_{3}}=1.78\times {{10}^{-5}})\]     [UPSEAT 2001]

    A)                 10.56 gm             

    B)                 15 gm

    C)                 12.74 gm             

    D)                 16.25 gm

    Correct Answer: A

    Solution :

               \[pOH=pKb+\log \frac{[Salt]}{[Base]}\]                    \[14-9.35=-\log (1.78\times {{10}^{-5}})+\log \frac{[Salt]}{100}\]                                 \[[Salt]=79.9\]Þ  \[\frac{w}{132}\times 1000=79.9\]Þ \[w=10.56\]


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