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KVPY Sample Paper KVPY Stream-SX Model Paper-18

  • question_answer
    90% of a first order reaction was completed in 100 min. The half-life of the reaction is

    A) 63.3 min

    B) 53.3 min

    C) 43.3 min

    D) 30 min

    Correct Answer: D

    Solution :

    For first order reaction \[t=\frac{2.303}{k}\log \frac{a}{a-x}\]
    For 90% reaction, \[100=\frac{2.303}{k}\log \frac{100}{100-90}\]
    \[k=\frac{2.303}{100}\log 10\]
    \[k=0.023\]
    Also, \[{{t}_{1/2}}=\frac{0.693}{k}=\frac{0.693}{0.023}=30.1\min \]


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