Question

Calculate the average atomic mass for element X(please help)

Answer 1

Wt Avg At Mass = 39.0229 amu

Step-by-step explanation:

The Weight Average Atomic Mass in atomic mass units (amu) is the sum of the Weight Average Mass contributions of each isotopic mass. That is,

Wt. Avg. At. Mass (amu) = ∑ Wt. Avg. Contributions of each isotopic mass

Wt. Avg. Contribution = fractional abundance x isotopic mass(amu)

For this problem data:

Isotope %Abundance fractional Isotopic Wt Avg Isotopic

abundance mass(amu) Contribution (amu)

1 9.67% 0.0967 38 3.6746 amu

2 78.68% 0.7868 39 30.6852 amu

3 11.34% 0.1134 40 4.5360 amu

4 0.31% 0.0031 41 0.1271 amu

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Wt. Avg. Atomic Mass (amu) = ∑ Wt. Avg. Contributions = 39.0229 amu