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Chemical Kinetics question

2017 · Q92
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Chemical Kinetics question

2017 · Q92

NEETChemistryChemical KineticsMCQ+4 / −1
A first order reaction has a specific reaction rate of 10−-−2 sec−-−1. How much time will it take for 20 g of the reactant to reduce to 5 g?
  1. A
    138.6 sec
  2. B
    346.5 sec
  3. C
    693.0 sec
  4. D
    238.6 sec
View written solutionFree

Correct answer: A

For a first order reaction,

k = 2.303tlog⁡[A]0[A]t{{2.303} \over t}\log {{{{\left[ A \right]}_0}} \over {{{\left[ A \right]}_t}}}t2.303​log[A]t​[A]0​​

⇒\Rightarrow⇒ 10-2 = 2.303tlog⁡205{{2.303} \over t}\log {{20} \over 5}t2.303​log520​

⇒\Rightarrow⇒ t = 138.6 sec

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