A rock contains 260. µmol 238U (t1/2 = 4.5 109 yr) and 114 µmol 206Pb. the 206Pb comes from 238U?
A rock contains 260. µmol 238U (t1/2 = 4.5 109 yr) and 114 µmol 206Pb. Assuming that all the 206Pb comes from decay of the 238U, estimate the rock's age in years
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amount of U present now = 26o * 238 *0.000001 = 0.061884
amount of Pb = 206* 114 * 0.000001 = 0.023484
original amount of U = 0.06188+ 238/ 206 * 0.023484
= 0.0890 gram
k = 0.693/ 4.5 * 0.000000001
= 1.54* 0.0000000001
t = 2.303*10000000000/ 1.54 log 0.0890/ 0.06188
= 2.360 * 1000000000 years