Question

What is the atomic mass of copper which is found to have two isotopes, if 69.1% of copper has a mass of 62,93 amu and the rest has 64.93amu?

Answer 1

To calculate the atomic mass of copper (Cu) considering its isotopes, you can use the weighted average formula. The formula is:

Atomic mass = (% abundance isotope 1 × mass isotope 1) + (% abundance isotope 2 × mass isotope 2) + ...

Let's denote the two isotopes of copper as Cu-63 and Cu-65.

Given: Abundance of Cu-63 = 69.1% Abundance of Cu-65 = 100% - 69.1% = 30.9% Mass of Cu-63 = 62.93 amu Mass of Cu-65 = 64.93 amu

Using the weighted average formula, we can calculate the atomic mass:

Atomic mass = (0.691 × 62.93 amu) + (0.309 × 64.93 amu) = 43.42433 amu + 20.06337 amu = 63.4877 amu

Therefore, the atomic mass of copper (Cu) is approximately 63.4877 amu.