chemistry

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How long will it take for the 100mg of cesium-137 to decay to 6.25mg(1/16 the original amount)?

  • chemistry -

    2n = 16
    Solve for n = number of half lives.

  • chemistry -

    still i can't understand it

  • chemistry -

    Do you have the half-life given in the problem or are you allowed to look it up? If so there is an easier way to set it up.
    To solve 2n = 16, take the log of both sides.
    log 2n = log 16
    n*log 2 = log 16
    n*0.301 = 1.2 etc.

    There is another way. Remember that half-life means the time it takes for 1/2 the material to disappear. So make a table like this. The periods are used for spacing.
    amount......# half-lives
    100 mg.........0
    50 mg..........1
    25 mg..........2
    12.5 mg........3
    6.25 mg........4
    So whatever the half-life is, multiply that by 4 and you will have the time it takes to go through 4 half-lives.

  • chemistry -

    thanks alot , this answer really helped me to understand this question

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