Posted by **Matt** on Thursday, May 21, 2009 at 3:46pm.

The age of a rock can be estimated by measuring the amount of 40Ar trapped inside. The calculation is based on the fact that 40K decays to 40Ar by a first-order process. It also assumes that none of the 40Ar produced by the reaction has escaped from the rock since it was formed.

40K + e- -> 40Ar k = 5.81 X 10^-11 year^-1

Calculate the half-life of the radioactive decay.

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