If the rate constant of a reaction is 0.03 s^-1, how much time does it take for 7.2 mol L^-1 concentration of the reactant to get reduced to 0.9 mol L^-1?(Given: log 2 = 0.301)

1. 69.3 s

2. 23.1 s

3. 210 s

4. 21.0 s

Doubtly Asked 30 Oct 2026 NEET UG 2025 Practice test neet Save WhatsApp Report

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Answer: 1. 69.3 s

Key idea: the unit \(\mathrm{s^{-1}}\) means first order: \(t=\frac{2.303}{k}\log\frac{[A]_0}{[A]}\).

Option (1). Check: 8 = \(2^3\) means three half-lives, \(3\times23.1=69.3\) s.

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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