Question

calculate the atomic mass of copper if copper -63 is 69.17% abundant and copper-65 is 30.83% abundant.

Answer 1

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:

1. For Cu-63:
\[
0.6917 \times 63 = 43.1211
\]

2. 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**.