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Thread: Chemistry and Exponential Models

  1. March 25th 2009, 01:58 PM #1
    cheer4life1694
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    Chemistry and Exponential Models

    Radium-221 has a half-life of 30 seconds. How long will it take for 77% of a sample to decay?
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  2. March 25th 2009, 02:31 PM #2
    skeeter
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    Quote Originally Posted by cheer4life1694 View Post
    Radium-221 has a half-life of 30 seconds. How long will it take for 77% of a sample to decay?
    y = fraction of substance left after time t

    h = half-life in same units as t

    y = \left(\frac{1}{2}\right)^{\frac{t}{h}}
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