JEE Main202622 January 2026Morning ShiftChemistryChemical KineticsActual
A product (First order reaction). Three sets of experiment were performed for a reaction under similar experimental conditions: Run 1 100 ~mL of 10 M solution of reactant A Run 2 200 ~mL of 10 M solution of reactant A Run 3 100 ~mL of 10 M solution of reactant A +100 ~mL of H ₂ O added. The correct variation of rate of reaction is
Options
- ARun 1< Run 2< Run 3
- BRun 3< Run 1< Run 2
- CRun 3< Run 1 = Run 2
- DRun 1= Run 2= Run 3
Correct answer
C. Run 3< Run 1 = Run 2
Step-by-step solution
For a first-order reaction, rate = k[A] , where rate is directly proportional to reactant concentration. Run 1: 100 mL of 10 M solution Concentration = 10 M Rate: r₁ = k 10 Run 2: 200 mL of 10 M solution Concentration remains 10 M (increasing volume doesn't change concentration) Rate: r₂ = k 10 Therefore r₁ = r₂ Run 3: 100 mL of 10 M solution + 100 mL of H₂O Total moles of A = 10 M × 0.1 L = 1 mol Total volume = 0.2 L New concentration = 1 mol / 0.2 L = 5 M Rate: r₃ = k 5 Therefore r₃ < r₁ = r₂