Uranium has three common isotopes. If the abundance of 234U is 0.0054%, the abundance of 235U is 0.7204% and the abundance of 238U is 99.2742%, what is the average atomic mass of uranium?

237.9 amu

Explanation:

Given data:

Abundance of U-234 = 0.0054 %

Abundance of  U-235 = 0.7204%

Abundance of  U-238 = 99.2742%

Average atomic mass = ?

Solution:

Average atomic mass = (abundance of 1st isotope × its atomic mass) +(abundance of 2nd isotope × its atomic mass) + (abundance of 3rd isotope × its atomic mass  / 100

Average atomic mass = (0.0054×234)+(0.7204×235) +(99.2742×238)  /100

Average atomic mass =  1.2636+ 169.294+ 23627.2596 / 100

Average atomic mass = 23797.8172/ 100

Average atomic mass = 237.9 amu.