# How to find abundance of 206, 207 and 208 Pb

by subopolois
Tags: abundance
 P: 69 how would i find the abundance of Pb 206, 207 and 208 if im given the isotopic data of 207Pb/206Pb and 208Pb/206Pb?
 Sci Advisor HW Helper PF Gold P: 3,724 Pending...
 Sci Advisor HW Helper PF Gold P: 3,724 OK... Assume that the expression 206Pb means the molar fraction of lead-206. The same is true for 207Pb and 208Pb. You know that the molar fractions sum to 1 as well as the molar ratios of 207Pb/206Pb and 208Pb/206Pb. You can also calculate 207Pb/208Pb. From here it is merely solving for the simultaneous equations.
P: 69
How to find abundance of 206, 207 and 208 Pb

 Quote by chemisttree OK... Assume that the expression 206Pb means the molar fraction of lead-206. The same is true for 207Pb and 208Pb. You know that the molar fractions sum to 1 as well as the molar ratios of 207Pb/206Pb and 208Pb/206Pb. You can also calculate 207Pb/208Pb. From here it is merely solving for the simultaneous equations.
ok, i think i get it. heres my scenerio,
the Pb content is 468ppm
207Pb/206Pb= 0.2515
208Pb/206Pb= 0.0581
i could just use abgebra to find each right?
206=x
207=0.2515x
208=0.0581x
i just solve for x and put it back into the previous equation?
HW Helper
PF Gold
P: 3,724
 Quote by subopolois ok, i think i get it. heres my scenerio, the Pb content is 468ppm 207Pb/206Pb= 0.2515 208Pb/206Pb= 0.0581 i could just use abgebra to find each right? 206=x 207=0.2515x 208=0.0581x i just solve for x and put it back into the previous equation?
I would use the definition... 206Pb + 207Pb + 208Pb = 1

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