Question

atomic mass practice

1. which isotope of copper is more abundant: copper - 63 or copper - 65? (the atomic mass of copper is 63.546 amu)
2. element x has two natural isotopes. the isotope with a mass of 10.012 amu (¹⁰x) has a relative abundance of 19.91%. the isotope with a mass of 11.009 amu (¹¹x) has a relative abundance of 80.09%. calculate the atomic mass of this element.
3. calculate the atomic mass of bromine. the two isotopes of bromine have atomic masses and relative abundance of 78.92 amu (50.69%) and 80.92 amu (49.31%).

Explanation:

Step1: Calculate the contribution of each isotope

For \(^{10}X\): \(10.012\times0.1991 = 1.9933892\)
For \(^{11}X\): \(11.009\times0.8009 = 8.8171081\)

Step2: Sum the contributions

\(1.9933892+8.8171081 = 10.8104973\approx10.81\)

Answer:

\(10.81\) amu