Question

a sample of magnesium contains the following relative abundances of its isotop
isotope | relative abundance
$_{12}^{24}$mg | 78.99%
$_{12}^{25}$mg | 10.00%
$_{12}^{26}$mg | 11.01%
what is the average relative atomic mass of the magnesium in the sample?

Explanation:

Step1: Convert percentages to decimals

For \(^{24}_{12}\text{Mg}\): \(78.99\% = 0.7899\)
For \(^{25}_{12}\text{Mg}\): \(10.00\% = 0.1000\)
For \(^{26}_{12}\text{Mg}\): \(11.01\% = 0.1101\)

Step2: Multiply each isotope's mass by its abundance

\(^{24}_{12}\text{Mg}\): \(24\times0.7899 = 18.9576\)
\(^{25}_{12}\text{Mg}\): \(25\times0.1000 = 2.5\)
\(^{26}_{12}\text{Mg}\): \(26\times0.1101 = 2.8626\)

Step3: Sum the results

\(18.9576 + 2.5 + 2.8626 = 24.3202\)

Answer:

\(24.32\) (rounded to two decimal places, or as per significant figures requirements)