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Finding the Age of a Rock Using Radioactive Decay Data

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(1) The half life of U-238 is 4.51x10^9 yrs. In a rock containing N atoms of U-238, how many Helium atoms are produced by radioactive decay of U-238 to Pb-206 in 4.51x10^9 yrs?

(2) A rock is analyzed for its helium and uranium content and found to contain 1.00x10^-9 mole of U-238 atoms, and 2.00x10^-9 mole of Helium atoms. Assuming that all of the helium was formed by radioactive decay of U-238 to Pb-206 and that it all remained trapped in the rock, how many moles of U-238 atoms were there when the rock was formed?

(3) Calculate the age of the rock?

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Solution Summary

The solution shows the calculations required to find the age of a rock using data such as moles U-238 remaining and helium formed.