Question

How would the following problem be set up: Average Atomic Mass of Zinc which has 5 stable isotopes Zn-64, Zn-66, Zn-67, Zn-68, Zn-70 with percent abundances in order, 49.2%, 27.7%, 4.0%, 18.5%, and .6%.

Answer 1

To find the average atomic mass of zinc, multiply the atomic mass of each isotope by its decimal abundance and sum the values. The final result gives the weighted average atomic mass reflecting the isotopes' natural abundances.

Step-by-step explanation:

To calculate the average atomic mass of zinc, which has five stable isotopes with given percent abundances, you need to multiply the mass of each isotope by its abundance (converted into decimal form) and sum the results. For example, with Zn-64, you would take 64 amu (its atomic mass) and multiply it by 0.492 (its abundance in decimal form). You do this for each isotope, then add all these products together to get the weighted average atomic mass for zinc.

The formula is: (Mass of isotope 1 × Abundance of isotope 1) + (Mass of isotope 2 × Abundance of isotope 2) + ... up to isotope 5. The resulting sum is the average atomic mass of zinc.

Using the provided abundances, the setup would look like this:

• (64 amu × 0.492) + (66 amu × 0.277) + (67 amu × 0.040) + (68 amu × 0.185) + (70 amu × 0.006)

Perform each multiplication, then sum the results to find the average atomic mass of zinc. It's essential to use these numbers since they reflect the isotopes' weighted contribution based on their natural abundance.