Monday, June 4

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All Sections: Follow all instructions carefully. Below you will find some information on half-life; look it over. When you are done, complete the worksheet on half-life, which can be found in the 'Homework' section (the answer to number one is 1.125 grams).

-HALF-LIFE is the time that it takes for 1/2 a sample to decompose.

-The rate of a nuclear transformation depends only on the “reactant” concentration.

Here's a graph of the half-life of the Oxygen-15 isotope:

For each duration (half-life), one half of the substance decomposes.

For example: Ra-234 has a half-life of 3.6 days. If you start with 50 grams of Ra-234 after 3.6 days you will have 25 grams left. After 7.2 days, 12.5 grams and after 10.8 days, 6.25 grams, and so on.

Here's another sample problem and answer:

Q: The half life of I-123 is 13 hr. How much of a 64 mg sample of I-123 is left after 39 hours?

A: 39/13 = 3...1 half life, 64 > 32. 2nd half life, 32 >16. 3rd half life 16 > 8mg