Nuclear Half-life Q&A Questions 9 c) & d)

The daughter product in this decay is

lead-207. What percentage of the total

possible amount of lead-207 has been

produced after 1420 million years?

Uranium 235 has a half-life of 710 million years. 1420 million years is 2 half-lives. There’d be about 75 percent of lead 207 produced. Uranium 235 = 25%, Lead 207 = 75% adding up to 100%

What percentage of uranium-235

remains after three half-lives?

After three half-lives, 12.5% of uranium-235 remains. 100% x 0.5 × 0.5 × 0.5 = 12.5%

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