Chemistry Target 1.6
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Explain the relative abundance of isotopes and how it is used to calculate atomic mass
A.
An element has an atomic number of 26 and has isotopes with mass numbers of 56 and 54. Its average atomic mass is 55.845 amu. Based on the average atomic mass, which of the following isotopes is most abundant?
- The isotope with a mass number of 54
- The isotope with a mass number of 56
- Both isotopes have equal abundances
- An isotope with a mass number other than 56 or 54
C.
Which statement correctly describes the average atomic mass of an element?
- The average of the two most abundant isotopes of an element
- The average of all of the naturally-occurring atomic mass values of isotopes
- The atomic mass of the most abundant isotope of an element
- The atomic mass of the least abundant isotope of an element
D.
E.
Which combination of abundances and atomic masses would lead to sulfur's average atomic mass of 32.065 amu?
- 90% S-32 and 10% S-33
- 93% S-32 and 7% S-33
- 75% S-32 and 25% S-33
- 85% S-32 and 15% S-33
F.
Mg has three different isotopes. Mg-24 has an abundance of 78.70%, Mg-25 has an abundance of 10.13%, and Mg-26 has an abundance of 11.17%. Which setup is correct for calculating the atomic mass of magnesium?
- (78.70)(24 u)+(10.13)(25 u)+(11.17)(26 u)
- (78.70)(24 u)+(11.17)(25 u)+(10.13)(26 u)
- (0.7870)(24 u)+(0.1013)(25 u)+(0.1117)(26 u)
- (0.7870)(24 u)+(0.1117)(25 u)+(0.1013)(26 u)