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NEET Sample Paper NEET Sample Test Paper-68

  • question_answer
    A first-order reaction completes its \[10%\] in 20 minutes then time required to complete its \[19%\] is

    A) 30 minutes                    

    B) 40 minutes

    C) 50 minutes                    

    D) 38 minutes

    Correct Answer: B

    Solution :

    In first phase, \[K=\frac{2.303}{20}\log \,\frac{90}{100}\]             ?. (i) In second phase, \[K=\frac{2.303}{t}\,\log \,\frac{81}{100}\]         ? (ii) From eq. (i) \[\frac{2.303}{20}\,\log \,\frac{90}{100}\,=\,\,\frac{2.303}{t}\,\log \,\,\frac{81}{100}\] \[t=\frac{20\left( log\,81-log\,100 \right)}{(log\,\,90-\log \,\,100)}\] \[=\frac{20(1.908-2)}{(1.954-2)}=\frac{20\times (-0.092)}{(-0.046)}\,\,=\,\,40\,\,\min \]


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