The <em>average</em><em> </em>atomic mass of element X that has two isotopes (one of 45.0 amu mass and 45% abundance and the other of 47.0 amu mass and 55.0% abundance) is 46.1 amu (option 1).
The <em>average </em>atomic mass (A) of element X can be calculated as follows:
(1)
Where:
m₁: is the mass of isotope 1 = 45.0 amu
m₂: is the <em>mass </em>of <em>isotope </em>2 = 47.0 amu
%₁: is the abundance percent of <em>isotope </em>1 = 45.0 %
%₂: is the <em>abundance percent</em> of <em>isotope </em>1 = 55.0 %
Hence, the <u>average atomic mass</u> is (eq 1):
Therefore, the <em>average </em>atomic mass of element X is 46.1 amu (option 1).
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