Question

An element X has two naturally occurring isotopes: X-35 (abundance = 75.77%, mass = 34.968852 amu) and X-37 (abundance = 24.23%, mass = 36.965903 amu).
Calculate the weighted atomic mass of X. Also, identify the unknown element.

a) 39.948 amu Argon
b) 35.453 amu Chlorine
c) 79.904 amu Bromine
d) 32.066 amu Sulfur

Answer 1

Answer:

x = 35.453 amu.  CHLORINE

Explanation:

Abundance of X³⁵ = 75.77%

Abundance of X³⁷ = 24.23%

Atomic mass of X³⁵ = 34.968852 amu

Atomic mass of X³⁷ = 36.965903 amu

Average atomic mass = ?

Solution:

Average atomic mass of carbon = (abundance of 1st isotope × its atomic mass) +(abundance of 2nd isotope × its atomic mass)  / 100

Average atomic mass of carbon = (34.968852 × 75.77)+(36.965903 ×24.23) /100

Average atomic mass of carbon=  2649.59 + 895.684 / 100

Average atomic mass of carbon = 3545.274 / 100

Average atomic mass of carbon = 35.453 amu.

x = 35.453 amu.  CHLORINE