Chapter 4.3, Problem 23SSC

Interpretation Introduction

Interpretation: The atomic mass of copper needs to be determined if two isotopes Cu-63 and Cu-65 are $69.2\%$ and $30.8\%$ and have masses of $62.930amu$ and $64.928amu$ respectively.

Concept introduction: Isotope is the same number of protons and electrons but has a different number of neutrons in an atom of the same element. The atomic mass is the mass of all isotopes of the element that has been averaged together. The relative abundance is the percentage of atoms that have a specific atomic mass present in a naturally occurring element.

Answer to Problem 23SSC

The atomic mass of copper is $63.5amu$ .

Explanation of Solution

The mass contribution of isotope Cu-63 is $(mass)\times (percentabundance)=62.930amu\times 0.692amu=43.5amu$

The mass contribution of isotope Cu-65 is $(mass)\times (percentabundance)=64.928amu\times 0.308amu=20amu$

Thus, the atomic mass of copper (Cu) $=43.5amu+20amu=63.5amu$

Conclusion

Hence, $63.5amu$ is the atomic mass of copper.