Question

this exercise will lead you to verify that the average atomic mass of magnesium is 24.31 amu, based on the following information: isotope mass (amu) percent abundance 24mg 23.985042 78.99% 25mg 24.985837 10.00% 26mg 25.982593 11.01% what is the value: atomic mass x fractional abundance for 25mg? for now, report your answer to three decimal places. mass contribution of 24mg = 18.946 amu (3 of 5) show approach check

Explanation:

Step1: Convert percent abundance to fractional abundance

For \(^{24}\text{Mg}\), fractional abundance \(= 78.99\%=0.7899\); for \(^{25}\text{Mg}\), fractional abundance \( = 10.00\% = 0.1000\); for \(^{26}\text{Mg}\), fractional abundance \(=11.01\% = 0.1101\)

Step2: Calculate mass - contribution of \(^{25}\text{Mg}\)

Mass - contribution \(=\text{atomic mass}\times\text{fractional abundance}\). The atomic mass of \(^{25}\text{Mg}\) is \(24.985837\) amu and its fractional abundance is \(0.1000\). So, mass - contribution \(=24.985837\times0.1000 = 2.4985837\) amu

Step3: Round the result

Rounding \(2.4985837\) amu to three decimal places gives \(2.499\) amu

Answer:

\(2.499\) amu