Uranium-232 has a half-life of 68.8 years. After 344.0 years, how much uranium-232 will remain from a 100.0-g sample?

The sample undergoes 344.0 ÷ 68.8 = 5 half-lives. Each half-life cuts the remaining mass in half, so 100.0 g × (1/2)^5 = 3.125 g, which rounds to 3.13 g. The correct choice is 3.13 g.

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