MHT CET Chemistry Question (2026) — Solution

Step-by-step solution

For a first order reaction, the rate constant is given by k = 2.303 t ( a a-x ) For 60\% completion in 20 minutes: k = 2.303 20 ( 100 100-60 ) = 2.303 20 (2.5) For 84\% completion in time t: k = 2.303 t ( 100 100-84 ) = 2.303 t (6.25) Equating the two expressions for k: 1 20 (2.5) = 1 t (2.5^2) 1 20 (2.5) = 2 t (2.5) t = 40 min Answer: 40 min