Question

Use the following data, calculate the average atomic mass of magnesium.
24 12Mg. – 78.70%

25 12Mg -- 10.13%

26 12Mg. -- 11.17%

Answer 1

Explanation:

If the abundance are as stated:

78.99% of 23.98504 u

10.00% of 24.98584 u

11.01% of 25.98259 u

I would check that the percentage values equal 100:

78.99 + 10.00 + 11.01 = 100

Which they do, and then just use "ratio maths":

(0.7899 x 23.98504) + (0.100 x 24.98584) + (0.1101 x 25.98259) = 24.30505 u

A quick check on Google shows: 24.305 u ± 0.0006 u

And so the answer looks right.

Here is an interesting question: Why does Google give 24.305 u ± 0.0006 u?