The iodine-131 nuclide has a half-life of 8.0 days. If you originally have a sample containing 728-g of I-131, after 6.86 weeks you will have

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To find the remaining amount of I-131 after 6.86 weeks, we first convert weeks to days: 6.86 weeks * 7 days/week = 48.02 days. Then, we use the half-life formula, dividing the total time by the half-life period: 48.02 days / 8 days/half-life = 6.0025 half-lives. The amount remaining after n half-lives is given by the initial amount times (1/2)^n. So, the remaining amount is 728g * (1/2)^6.0025 ≈ 11.4g.

The Iodine-131 Nuclide Has a Half-Life of 8