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The half-life of Iodine - 131 is approximately 8 days, which means the mass of a sample of iodine decays by half every 8 days. The amount remaining can

 

be calculated using the formula i = 1600 * 2 ^ -t/8 , where t is the time in days since the beginning of the sample.

 

a) Write down this formula without negative exponents.

 

 

b)Find the amount of material remaining after 4 days as an exact and approximate value.

 Jul 3, 2019
 #1
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a) i = 1600 * 1/2^(t/8)

 

b) i = 1600 * 1/2^(1/2)

     i = 1600 * 0.7071067812......

     i =1,131.37 - grams remaining after 4 days(Exactly)

Since half-life is 8 days, it therefore means that in 4 days about 1/4 of 1600 would have decayed, or:

1600 - 400  = 1,200 grams (approx.) would remain after 4 days. 

 Jul 3, 2019
 #2
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Thanks! smiley

Guest Jul 4, 2019

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