Chemistry

Question

A 160g radioactive sample is left undisturbed for 12.5 hours. At the end of that period, only 5.0g remain. What is the half-life of this sample? Show work

2 Answer

  • it would be 26 because once you divide 160g by 5.0g and add 12.5 you would get 26

    hope this helps

  • Answer:

    2.50 h  

    Step-by-step explanation:

    The half-life of a sample is the time it takes for half of it to decay.  

    After one half-life, half (50 %) of the original amount will remain.  

    After a second half-life, half of that amount (25 %) will remain, and so on.  

    We can construct a table as follows:  

      No. of      Fraction          Mass

    half-lives  remaining   Remaining/g

          1                 ½                  80

          2                ¼                  40

          3                ⅛                  20

          4                ¹/₁₆                 10

          5                ¹/₃₂                 5.0

          6                ¹/₆₄                 2.5

    We see that 5.0 g remain after five half-lives.

    5t_½ = 12.5 h     Divide each side by 5

     t_½ = 2.50 h

    The half-life is 2.50 h.

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