Asked by Vanessa

Copper is composed of two naturally occurring isotopes: Cu−63 (69.170%) and Cu−65. The ratio of the masses of the two isotopes is 1.0318.
Answered by Vanessa
What is the mass of Cu−63?
Answered by DrBob222
I believe you also need to know the mass of the mixture occurring in nature.
Answered by Vanessa
I just asks me to figure out the mass of Cu-63? the mass of nature is 69.170% for Cu-63 and for Cu_65 it is 30.83%
Answered by DrBob222
I don't think you understand what I need. The ABUNDANCE of 63 is 69.170% and the ABUNDANCE of 65 is 30.83%. But you don't have the mass of anything; i.e., you don't have the mass of 63 or the mass of 65 or the mass of the isotope as it occurs in nature (the mixture). Here is as far as I can go.
Let x = mass Cu63
and y = mass Cu65
and z = mass of naturally occurring isotope.
--------------------
x(0.69170)+(y)(0.3083) = z
Three unknowns and you can't solve the equation. You can relate x and y with the ratio data. You don't say which ratio is which but I presume that is mass Cu65/mass Cu63 = 1.0318 and that lets us write
y/x = 1.0318 or y = 1.0318x and that can be substituted into the above for
x(0.69170) + (1.0318x)(0.3083)= z.
I believe you need another piece of information, namely z, to solve the equation.
Answered by Vanessa
would is be the atomic number for the element Cu?
Answered by Vanessa
That is all the information they gave me that is why I ask
Answered by DrBob222
No it isn't the atomic number; however, I looked up the atomic mass on the periodic table and it is 63.5463 as it occurs in nature. Plug that in for z and solve.
Answered by Vanessa
I got 16.99?
Answered by Vanessa
never mind its not that
Answered by Griffin
I have this same problem and have trying to figure it out forever, I have no idea how to solve this.
Answered by Cristian
The response written by DrBob is correct. Using a substitution method with the y=1.0318x, substitute the y in the original formula for 1.0318x, and solve. Keep in mind that you must set z=63.5463 (or just 63.55), otherwise you cannot hope to solve for the abundance of Cu-63.
Answered by Joon Chun
x*0.69170+x*1.0318*(1-0.69170)=63.546
x=answer
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