A first-order reaction has a rate constant . How many seconds does it take for the reactant concentration to decrease to 25% of its initial value? (Take )
Answer and explanation
Correct answer: B. 200 seconds
- Step 1: Half-life s. Step 2. Decreasing to 25% () requires exactly 2 half-lives. Step 3. Total time seconds. Answer: 200 seconds. Why not the others: Two half-lives of 100 seconds equal 200 seconds.
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