What is the Mass Ratio Between 12C and 13C Atoms?

[Lorek]

Homework Statement

What is the ratio of mass of a ¹²C atom to a ¹³C atom

The Attempt at a Solution

12.011/13 = .9239230769

Solution given at back of book = .92286

 

[Borek]

Why 12.011? Why 13?

 

[Lorek]

The atomic weight of C-12 is 12.011, the atomic weight of C-13 is 13. I divided the weight of C-12 by the weight of the C-13 to get a ratio.

 

[Borek]

12.011 is not an atomic weight of C-12, just like 35.45 is not a mass of Cl atom.

 

[Lorek]

Ok, I understand that the atomic weight's are weighted averages. I just used the atomic weight because it asks for a ratio between two atoms. As for how to set it up I don't have the slightest idea how to set it up, no example problems to model form, nor solution steps.