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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 remaining undecayed after 18 hours would be

Options

  1. A8.0 ~g
  2. B12.0 ~g
  3. C16.0 ~g
  4. D4.0 ~g

Correct answer

D. 4.0 ~g

Step-by-step solution

t _ 1 / 2 =3 hrs . Initial mass ( C ₀ )=256 ~g C _ n = C ₀ 2^ n = 256 (2)^6 = 256 64 =4 ~g

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