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Activity of naturally occurring potassium

The naturally occurring isotopes of Potassium are:

39K (abundance 93.10%)
40K (abundance 0.0118%)
41k (abundance 6.88%)

40 K is radioactive and decays by B-decay with a half life of 1.29 multiplied by 10^9 years.

Question: Using the definitions for the decay constant and for the Becquerel, calculate the activity of 1 gram of naturally occurring potassium.

(Note: 6.02 multiplied by 10^23 (i.e 1 mole) atoms of any element will have a mass in grams equal to its atomic weight, for example, 6.02 multiplied by 10^23 atoms of calcium will weigh 40.08 grams.)

Solution Summary

Activity of a given amount of radioactive material found in nature is calculated as the decay constant multiplied by the number of radioactive nuclei.

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