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The rate of a first-order reaction is 0.04 mol l⁻¹s⁻¹ at 10 seconds and 0.03 mol l⁻¹s⁻¹ at 20 seconds after initiation of the reaction. The half-life period of the reaction is

1. 24.1 s
2. 34.1 s
3. 44.1 s
4. 54.1 s

Correct answer: 34.1 s

Solution

For a first-order reaction, the rate constant (k) can be calculated using the equation: k = ln(N₀/N) / t, where N₀ is the initial concentration, N is the final concentration, and t is the time. Given the rates at two different times, we can calculate the rate constant and then use it to find the half-life period.

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