Posted by Candace on Saturday, June 30, 2012 at 4:22pm.
Naturally occurring cobalt consists of only one isotope Co59 whose relative atomic mass is 58.9332. A synthetic radioactive isotope of cobalt Co60, relative atomic mass 59.9338, is used in radiation therapy for cancer. A 1.8516 sample of cobalt has an apparent "atomic mass" of 58.9901.Find the mass Co60 of in this sample

chemistry  bobpursley, Saturday, June 30, 2012 at 4:58pm
58.9332*(1X)+59.9338*x=58.9901
solve for x, which is the decimal fraction of Co60, then multipy it by 1.8516 to get the mass of Co60 
chemistry  DrBob222, Saturday, June 30, 2012 at 4:59pm
Let x = fraction of Co60; then
1x = fraction of Co59.
mass Co59(1x) + mass Co60(x) = 58.9901
Solve for x (and multiply by 100 if you want percent, then
fraction x 1.8516g = mass Co 60 in the 1.8616g sample. 
chemistry  Candace, Saturday, June 30, 2012 at 7:09pm
When I worked it out I got .105 g, is that correct?

chemistry  Candace, Saturday, June 30, 2012 at 7:34pm
I have to get this question right, in order to make a B on my assignment

chemistry  DrBob222, Saturday, June 30, 2012 at 7:54pm
Yes.