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The half-life of a radioactive isotope is three hours. If the initial mass of the isotope were 256 g, the mass of it in grams remaining undecayed after 18 hours would be:

Correct answer

4

Step-by-step solution

t 1 / 2 = 3 hours, n = T / t 1 / 2 = 18 / 3 = 6 N = N 0 1 2 6 = 2 5 6 × 1 8 × 1 8 = 4 g ·

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