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Saturday, 31 October

JEE Main 2025 · ChemistryMultiple choiceDiagram basedMediumDiagram reading

JEE Main 2 April 2025, Shift 2, Chemistry Q56

Question 56 of 75 in this shift, Chemistry question 6 of 25, Section A.

Reactant A converts to product D through the given mechanism (with the net evolution of heat) : A→BA \rightarrow B slow; ΔH=+\Delta H = +ve B→CB \rightarrow C fast; ΔH=−\Delta H = -ve C→DC \rightarrow D fast; ΔH=−\Delta H = -ve Which of the following represents the above reaction mechanism ?

The figure, in words

Four energy vs reaction coordinate diagrams (A to D through intermediates B and C), given as options.
  1. (1)[figure: energy vs reaction coordinate; A low, first barrier highest, then two smaller barriers, D lowest]Official answer
  2. (2)[figure: energy vs reaction coordinate; A low, three barriers of increasing height, last barrier highest, D lower than A]
  3. (3)[figure: energy vs reaction coordinate; A lowest, very high first barrier, then two lower barriers, D at a level above A]
  4. (4)[figure: energy vs reaction coordinate; A low, high first barrier, smaller second barrier, high third barrier, D slightly above A]

Official answer

Option 1

NTA final key.

Chapter
Chemical Kinetics
Topic
Arrhenius Equation
Idea tested
Reaction Energy Profiles

Same idea in other shifts

Asked 4× in all
  1. 6 Apr 2023, Shift 2 · Q63Consider the following reaction that goes from A to B in three steps as shown below: Choose the correct option Number of intermediates |…MediumDiagram basedHas a figure
  2. 8 Apr 2023, Shift 2 · Q63The correct reaction profile diagram for a positive catalyst reaction.EasyDiagram basedHas a figure
  3. 31 Aug 2021, Shift 1 · Q53According to the following figure, the magnitude of the enthalpy change of the reaction A+B→M+N\mathrm{A+B\rightarrow M+N} in kJ mol−1^{-1} is…MediumNumerical valueHas a figure

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. This question needs a figure we do not reproduce; it is described in words above. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.