Sodium-24 has a half-life of 15.0 hours. Suppose you had a sample containing 0.010 moles of Na-24. How many hours would be required to reduce your sample to 6.25 × 10^{− 4} moles? A)120 B)60 C)45 D)30

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Quizplus · Accepted Answer

The sample reduces to 6.25 × 10^−4 moles, which is 1/16th of the original amount. This requires 4 half-lives (since 1/2^4 = 1/16). Each half-life is 15 hours, so 4 half-lives take 60 hours.

Sodium-24 Has a Half-Life of 15