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JEE Main201910 Jan 2019Evening ShiftChemistryChemical KineticsActual

For an elementary chemical reaction, A 2 ⇄ k - 1 k 1 2 A , the expression for d A dt is:

Options

  1. A2 k 1 A 2 - 2 k - 1 A 2
  2. B2 k 1 A 2 - k - 1 A 2
  3. Ck 1 A 2 + k - 1 A 2
  4. Dk 1 A 2 - k - 1 A 2

Correct answer

A. 2 k 1 A 2 - 2 k - 1 A 2

Step-by-step solution

For the reaction, A 2 → K 1 2 A r f = - d A 2 dt = 1 2 d A dt 1 = K 1 A 2 d A dt 1 = 2 K 1 A 2 For the reaction, 2 A → k - 1   A 2 r b = - 1 2 d A dt 2 = K - 1 A 2 d A dt 2 = - 2 K - 1 A 2 Hence, the overall rate is given by: d A dt = 2 k 1 A 2 - 2 k - 1 A 2

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