a sample of potassium is composed of 23% k-39, 48% k-40 and the remainder k-41. calculate the average mass
of the sample.

Explanation:

The atomic mass is the weighted average of the atomic masses of each isotope.

In a weighted average, we multiply each value by a number representing its relative importance.

In this problem, the percent abundance represents the relative importance of each isotope.

Data:

K-39 = 23 %

K-40 = 48 %

Calculations:

(a) Calculate %  K-41

K-41 = 100 - 23 - 48 = 29 %

(b) Calculate atomic mass of sample