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KCET2012ChemistryChemical Kinetics

A first order reaction is 60 % complete in 20 minutes. How long will the reaction take to be 84 % complete?

Options

  1. A68 ~min
  2. B40 ~min
  3. C76 ~min
  4. D54 ~min

Correct answer

B. 40 ~min

Step-by-step solution

For a first order reaction, k= 2.303 t a a-x I Case k= 2.303 20 100 100-60 = 2.303 20 100 40 aligned &= 2.303 20 ( 10- 4) &= 2.303 20 (1-0.6020)=0.046 aligned II Case aligned k &= 2.303 t 100 100-84 t=& 2.303 0.046 100 16 &= 2.303 0.046 ( 100- 16) &= 2.303 0.046 (2-1.2041) &=39.84 ~min =40 ~min aligned

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