Question
For a first order reaction A B t/ min [A]/M 0 0.6500 x 0.0650 20 0.00065 x= ______ min. (Nearest integer)
JEE Main
Chemistry
Chemical Kinetics
2026
JEE Main 2026 (04 April Shift 2)
JEE Main Chemistry Question (2026) — Solution
Options
- A. A
- B. B
- C. C
- D. D
Answer
A. A
Step-by-step solution
For a first order reaction, the rate constant k is given by: k = 1 t [A]_0 [A]_t Using the data at t = 20 min: k = 1 20 0.6500 0.00065 = 1 20 1000 = 3 20 10 Using the data at t = x min: k = 1 x 0.6500 0.0650 = 1 x 10 Equating the two expressions for k: 3 20 10 = 1 x 10 3 20 = 1 x x = 20 3 = 6.66... Rounding to the nearest integer, we get x = 7. Answer: 7
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