A moon rock collected by a U. S. Apollo mission is estimated to be 4.20 billion years old by uranium/lead dating. Assuming that the rock did not contain any lead when it was formed, what is the current mass of 206Pb per 1.305 g of 238U in the rock? The half-life of 238U is t1/2 = 4.47 * 109 years.

Question

Chemistry

Nehemiah Miller

28 April, 20:06

A moon rock collected by a U. S. Apollo mission is estimated to be 4.20 billion years old by uranium/lead dating. Assuming that the rock did not contain any lead when it was formed, what is the current mass of 206Pb per 1.305 g of 238U in the rock? The half-life of 238U is t1/2 = 4.47 * 109 years.

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Bryan Dean · Answer 1

We are given

4.20 billion yea old sample

1.305 g 238U

half life of 238U = 4.47 * 109 years

We are asked to get the mass of 206Pb

Assuming that 238U decays only to 206P, then

m = 1.305 (1/2) ^ (4.20x109 / 4.47x109)

Then, solve for m.