Chapter 2 - Sections 2.1-2.9 - Exercises - Cumulative Problems - Page 82: 100

$127.0541\ amu$

1. Compute the fractional abundance for each isotope $\frac{12.385\ g}{12.358\ g+1.0007\ g}= 0.9252$ $\frac{1.0007\ g}{12.358\ g+1.0007\ g}= 0.0748$ 2. Use a weighted average to compute the apparent atomic mass of the sample. $(0.9252)(126.9045\ amu)+(0.0748)(128.9050\ amu) = 127.0541\ amu$