By knowing the natural abundance of minor isotopes, it's possible to calculate the relative heights of M+ and M+1 peaks. If natural abundances are 12C - 98.9% and 13C - 1.10%, what are the relative heights, to the nearest 0.1%, of the M+ and M+1 peaks in the mass spectrum of ribose, C5H10O5?

Question

By knowing the natural abundance of minor isotopes, it's possible to calculate the relative heights of M+ and M+1 peaks. If natural abundances are 12C - 98.9% and 13C - 1.10%, what are the relative heights, to the nearest 0.1%, of the M+ and M+1 peaks in the mass spectrum of ribose, C5H10O5?
Ignore the contributions of isotopes like 2H (deuterium; 0.015% natural abundance) and 17O (0.04% natural abundance) that are small.

I added up the different masses and got 103% but that isn't correct.

DrBob222 · Answer

I took a swing at this a few days ago. Was that not right?