Question

32. 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.

Answer 1

40.06 amu.

Step-by-step explanation:

From the question given above, the following data were obtained:

Isotope A (K-39)

Mass of A = 39 amu

Abundance of A = 23%

Isotope B (K-40)

Mass of B = 40 amu

Abundance of B = 48%

Isotope C (K-41)

Mass of C = 41 amu

Abundance of C = 100 – (23 + 48)

Abundance of C = 100 – 71

Abundance of C = 29%

Average mass =?

Average mass = [(Mass of A × A%)/100] + [(Mass of B × B%)/100] + [(Mass of C × C%)/100]

= [(39 × 23)/100] + [(40 × 48)/100] + [(41 × 29)/100]

= 8.97 + 19.2 + 11.89

= 40.06 amu

Thus, the average mass of potassium is 40.06 amu