chemistry

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a radioactive substance decays 10% in 5 days. The amount remains after 20 days?

  • chemistry -

    You need to determine k, the rate constant and I would do it this way.
    ln(No/N) = kt
    No = 10
    N = 90
    k = solve for this
    t = 5 days.

    Then knowing k, redo
    ln(No/N) = kt
    No = 100
    N = Solve for this.
    k from above
    t = 20 days

  • chemistry -

    How

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