Chem

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Radioactive 24Na with a half-life of 14.8 hours is injected into an animal in a tracer experiment. How many hours will it take for the radioactivity to fall to 12.5% of its original intensity?

I am confused on what number to start with

  • Chem -

    You have the half life, Use that to calculate k.
    k = 0.693/t1/2

    Then
    ln(No/N) = kt
    Use 100 for No
    Use 12.5 for N
    Substitute k from above.
    Solve for t in hours if you use t1/2 in hours.

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