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ChemistryJEE Main 23 Jan 2026, Shift 2·Q11·MCQ·Easy–moderate

Chemical Kinetics · Rate of reaction and rate constant

Observe the following reactions at T(K)
  • (I)A→products\ce{A -> products}.
  • (II)5 BrX−(aq)+BrOX3X−(aq)+6 HX+(aq)→3 BrX2(aq)+3 HX2O\ce{5Br^- (aq) + BrO3^- (aq) + 6H^+ (aq) -> 3Br2 (aq) + 3H2O} (ll)
Both the reactions are started at 10.00 am. The rates of these reactions at 10.10 am are same. The value of −Δ[Br−]Δt-\dfrac{\Delta[\mathrm{Br^-}]}{\Delta t} at 10.10 am is 2×10−42\times10^{-4} mol L−1^{-1} min−1^{-1}. The concentration of A at 10.10 am is 10−210^{-2} mol L−1^{-1}. What is the first order rate constant (in min−1^{-1}) of reaction I?
  1. (1)2×10−32\times10^{-3}
  2. (2)10−310^{-3}
  3. (3)10−210^{-2}
  4. (4)4×10−34\times10^{-3}
We corrected a printing error in the original paper

Source printed the unit as “mol L−1^{-1} Min−1^{-1}”.

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See the full 23 Jan 2026, Shift 2 paper