NEET Sample Paper NEET Sample Test Paper-25

  • question_answer
    The reaction \[A\to B\]follows first-order kinetics. The time taken for 0.8 mole of A to produce 0.6 mole of B is 1 hr. What is the time taken for conversion of 0.9 mole of A to produce 0.675 mole of B?

    A)  1 hr

    B)  0.5 hr

    C)  0.25 hr

    D)  2 hr

    Correct Answer: A

    Solution :

     For the reaction \[2A+B\to 3C+D\] Rate constant of first-order reaction \[k=\frac{2.303}{t}{{\log }_{10}}\frac{{{(A)}_{0}}}{{{(A)}_{t}}}\]or\[k=\frac{2.303}{1}\times {{\log }_{10}}\frac{0.8}{0.2}\]  (i) (because 0.6 mole of 5 is formed) Suppose \[{{t}_{1}}\] hour is required for changing the con- centration of A from 0.9 mole to 0.675 mole of B. Remaining mole of A = 0.9 - 0.675 = 0.225 \[\therefore \]      \[k=\frac{2.303}{t}{{\log }_{10}}\frac{0.9}{0.225}\]                     (ii) From Eqs (i) and (ii) \[k=\frac{2.303}{t}{{\log }_{10}}\frac{0.8}{0.2}=\frac{2.303}{{{t}_{1}}}{{\log }_{10}}\frac{0.9}{0.225}\] \[2.303\,{{\log }_{10}}4=\frac{2.303}{t}{{\log }_{10}}4\]


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