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Chemical Kinetics question

2019 · Q84
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Chemical Kinetics question

2019 · Q84

NEETChemistryChemical KineticsMCQ+4 / −1
If the rate constant for a first order reaction is k, the time (t) required for the completion of 99 % of the reaction is given by :
  1. A
    t=4.606kt = {{4.606} \over k}t=k4.606​
  2. B
    t=2.303kt = {{2.303} \over k}t=k2.303​
  3. C
    t=0.693kt = {{0.693} \over k}t=k0.693​
  4. D
    t=6.909kt = {{6.909} \over k}t=k6.909​
View written solutionFree

Correct answer: A

For a first order reaction,

t = 2.303klog⁡[A0][A]{{2.303} \over k}\log {{\left[ {{A_0}} \right]} \over {\left[ A \right]}}k2.303​log[A][A0​]​

for 99% completion of the reaction,

t=2.303klog⁡100100−99t = {{2.303} \over k}\log {{100} \over {100 - 99}}t=k2.303​log100−99100​

⇒\Rightarrow⇒ t=4.606kt = {{4.606} \over k}t=k4.606​

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