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Homework Help: Decay contant of xenon and strontium

  1. Nov 20, 2009 #1
    1. The problem statement, all variables and given/known data

    The decay constant of xenon-142 is 0.462(s^-1), and the decay constant of strontium-90 is 7.85*10^-10 (s^-1). Initially, a sample of radioactive waste material contains equal numbers of strontium-90 and xenon-142 nuclei.

    Calculate the time taken for the ratio: number of strontium-90 nuclei/number of xenon-142 nuclei to become equal to 1.20*10^6.

    2. Relevant equations

    Not sure

    3. The attempt at a solution

    Not sure, please help!
  2. jcsd
  3. Nov 20, 2009 #2


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    Homework Helper

    Have you seen the formula N=N0*e^(-kt)? Write out a formula for xenon, a formula for strontium, and a formula for the strontium:xenon ratio. The reason for doing this is that you know this ratio's numerical value and can set it equal to the formula.
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