Question

How to find the relative atomic mass?

Can somebody please explain to me how to do question 9? How am I gonnna the mass if I don't know anything? Please help!

Answer 1

Use the percentage abundances to calculate the weighted average (relative) atomic mass of the sample.

Explanation:

The Area under each peak is proportional to the relative concentration of that isotope. It can be approximated by the height of the peak for similarly-shaped peaks. Your measurement scale may be different from mine, but the ratios should be the same.

I have peak heights of 19, 2, 2 for each isotope respectively. Therefore,
`.^(24)Mg = 19/23 = 0.826;`
`.^(25)Mg = 2/23 = 0.0870;`
`.^(26)Mg = 2/23 = 0.0870.`
These percentages are applied to the isotopic masses to find the “relative atomic mass” of the sample.
0.826 * 24 = 19.82 amu
0.087 * 25 = 2.18 amu
0.087 * 26 = 2.26 amu
The sum of these is the relative atomic mass of Mg in this sample. 24.26 g/mole.