A meteor contains 0.556 g of pb-206 to every 1.00 g of u-238. assuming that the meteor did not contain any pb-206 at the time of its formation, determine the age of the meteor. u-238 decays to pb-206 with t1/2 = 4.5 x 109 y

Answer is: 2,94·10⁹ years.

m (Pb) = 0,556 g.

n (Pb) = m:M = 0,556g:206g/mol = 0,0027mol.

m (Au) = 1,00g.

n (Au) = 1g:238g/mol = 0,0042mol.

n (Pb) / n (Au) = 0,575

t1/2 = 4,5·10⁹ years.

λ = 0,693:t1/2, λ = 0,693:4,5·10⁹ = 0,154·10⁻⁹.

λ-decay constant

Use this formula: λ·t = ln (1 + n (Pb) / n (Au)

ln - natural log.

t = 0,453:0,154·10⁻⁹ = 2,94·10⁹ years.