chemistry

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A radium-226 sample initially contains 0.112mol. How much radium-226 is left in the sample after 6400 years. The half-life of radium-226 is 1600 years.

  • chemistry -

    long way.
    k = 0.693/t1/2
    ln(No/N) = kt
    No = 0.112 mol
    N = unknown
    k from above.
    t = 6400 years.

    shorter way.
    0.112*(1/2^n)
    0.112*(1/2^6400/1600)
    0.112*(1/2^4) = N

  • chemistry -

    0.04 is the answer

  • chemistry -

    The half-life of Radium -226 is 1600 years. How much Ra 226 remains in a 30.0 g sample after 6400 years?

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