To calculate the atomic mass of copper using the abundances of its isotopes, we can use the following formula:
\[ \text{Atomic Mass} = \left( \text{abundance of Cu-63} \times \text{mass of Cu-63} \right) + \left( \text{abundance of Cu-65} \times \text{mass of Cu-65} \right) \]
Given:
- Abundance of Cu-63 = 69.17% = 0.6917 (as a fraction)
- Mass of Cu-63 = 63 amu
- Abundance of Cu-65 = 30.83% = 0.3083 (as a fraction)
- Mass of Cu-65 = 65 amu
Now we can substitute these values into the formula:
\[ \text{Atomic Mass} = (0.6917 \times 63) + (0.3083 \times 65) \]
Calculating each part:
-
For Cu-63: \[ 0.6917 \times 63 = 43.1211 \]
-
For Cu-65: \[ 0.3083 \times 65 = 20.0445 \]
Adding these results together:
\[ \text{Atomic Mass} = 43.1211 + 20.0445 = 63.1656 \]
Thus, the atomic mass of copper, based on the given isotopic abundances, is approximately 63.17 amu.