Question

Question 1 (1 point)

A new element has been discovered at Archer High School. The element symbol is Zz
and it has 2 naturally occurring isotopes.
The first isotope has a mass of 85.96 amu and a percent abundance of 87.20%.
The second isotope has a mass of 86.78 amu.
What is the average atomic mass of element Zz? Round to the hundredth's place
(0.01 or 2 decimal places).
Your Answer:
Answer
units

Answer 1

86.06 amu is the average atomic mass of element Zz.

Step-by-step explanation:

We may find the average atomic mass of Zz with a simple thought experiment. Let's imagine that we were given 100.0 grams of Zz. We know that 87.20% of that 100.0 grams is an isotope having 85.96 AMU (atomic mass units). That means the other 12.80% must be the isotope with 86.78 AMU.

Since we picked 100.0 grams, it is easy to see that we would have:

87.2 grams of 85.96 AMU, and

12.8 grams of 86.78 AMU

-----------

100.0 grams total

The contribution of each isotope can be calculated by taking it's percent abundance times it's AMU andf then adding the total results:

AMU % Contribution to total AMU

85.96 87.2 74.96

86.78 12.8 11.11

-------- --------- -----------

100.0 86.06 amu

The sum of the two weighted averaged amu numbers is the average atomic mass of element Zz. [Element Zz has a good futire as a sleep aid.]