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JEE Main & Advanced Sample Paper JEE Main Sample Paper-31

  • question_answer
    A buffer solution is prepared in which the concentration of \[N{{H}_{4}}^{+}\] is \[0.30\,M\] and the concentration of \[N{{H}_{4}}^{+}\] is \[0.20\,M\]. If the equation constant, \[{{K}_{b}}\] for \[N{{H}_{3}}\] equal to \[1.8\times {{10}^{-5}}\], what is the pH of this solution, \[(\log \,\,1.8=0.26)\]

    A) \[9.08\]         

    B)                                    \[9.43\]

    C) \[11.72\]            

    D)    \[8.73\]

    Correct Answer: B

    Solution :

    \[[N{{H}_{3}}]=0.3\,M[NH_{4}^{+}]=0.2\,\,m\] \[{{K}_{b}}=1.8\times {{10}^{-5}}\] \[{{P}^{OH}}=pKa+\log \frac{[salt]}{[base]}\] \[=4.74+0.3010-0.4771=4.56\] \[{{P}^{H}}=14-4.56=9.436\] \[\Delta {{T}_{b}}=i{{K}_{b}}.m\]


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