Question

Calculate the average atomic mass of element, X. A sample of X is 65.20% X-17, 13.50% X-18, and 21.30% X-19.

Answer 1

Answer:

The average atomic mass of element X is 17.561 u.

Explanation:

Average atomic mass of an element is defined as the sum of masses of each isotope each multiplied by their natural fractional abundance.

Formula used to calculate average atomic mass follows:

$\text{Average atomic mass }=\sum_{i=1}^n\text{(Atomic mass of an isotopes)}_i\times \text{(Fractional abundance})_i$ .....(1)

We are given:

Mass of isotope X-17 = 17 u

Percentage abundance of isotope X-17 = 65.20 %

Fractional abundance of isotope 1 = 0.6520

Mass of isotope X-18 = 18 u

Percentage abundance of isotope X-18 = 13.50 %

Fractional abundance of isotope X-18 = 0.1350

Mass of isotope X-19 = 19 u

Percentage abundance of isotope X-19 =21.30%

Fractional abundance of isotope X-19 = 0.2130

Putting values in equation 1, we get:

$\text{Average atomic mass of Z}=\sum[(17 u\times0.6520 )+(18 u\times 0.1350)+(19 u\times 0.2130)]$

$\text{Average atomic mass of Z}=17.561 u$