Question

Neptunium-239 has a half-life of 2.35 days. How many days must elapse for a sample of 239Np to decay to 0.100% of its original quantity

Answer 1

The half life equation is:
N(t)/N(0) = (1/2)^(t/2.35)

Solve for t when: N(t)/N(0) = 0.00100

Answer 2

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Answer 3

23.4 days