Multiple Choice
Calculate the atomic mass of element X given its isotopes X-45 with a mass of 44.8776 amu and 32.88% abundance, and X-47 with a mass of 46.9443 amu and 67.12% abundance.
2. Atoms & Elements
Atomic Mass
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Given the mass spectrum data of an element with isotopes having masses of 10 amu (20% abundance), 11 amu (50% abundance), and 12 amu (30% abundance), calculate the atomic weight and identify the element.
A
Oxygen
B
Carbon
C
Boron
D
Nitrogen
Verified step by step guidance1
Understand that the atomic weight of an element is the weighted average of the masses of its isotopes, based on their natural abundance.
For each isotope, multiply the mass of the isotope by its relative abundance (expressed as a decimal). For example, for the isotope with a mass of 10 amu and 20% abundance, calculate 10 amu * 0.20.
Repeat the calculation for the other isotopes: 11 amu with 50% abundance and 12 amu with 30% abundance. Use the expressions 11 amu * 0.50 and 12 amu * 0.30.
Add the results of these calculations together to find the weighted average, which represents the atomic weight of the element.
Compare the calculated atomic weight to known atomic weights of elements to identify the element. In this case, the calculated atomic weight should match that of Boron.
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