Question

What is the average isotopic mass of an element that has the following abundances in nature? Isotopic mass: X20 X22 X23 Abundances in natures: 90.5 % 8.0 % 1.5 %

Answer 1

Answer: 20.2

Step-by-step explanation:

Mass of isotope 1 = 20

% abundance of isotope 1 = 90.5% =
`(90.5)/(100)=0.905`

Mass of isotope 2 = 22

% abundance of isotope 2 = 8.0% =
`(8)/(100)=0.08`

Mass of isotope 3 = 23

% abundance of isotope 3 = 1.5% =
`(1.5)/(100)=0.015`

Formula used for average atomic mass of an element :

`\text{ Average atomic mass of an element}=\sum(\text{atomic mass of an isotopes}* {{\text { fractional abundance}})`

`A=\sum[(20* 0.905+(22* 0.08)+(23* 0.015]`

`A=20.2`

Therefore, the average atomic mass of the element is 20.2.