Answer to Question #92748 in Chemistry for Jenisha Patel

Question

Potassium (atomic mass = 30.19 amu) has three isotopes with masses 38.9367 amu, 39.9640 amu, and 40.9618 amu. The abundance of the last isotope is 6.73%. Estimate the abundances of the other two isotopes

Answer 1

FIrst of all question should be changed. the atomic mass can not be less than all individual isotopes. and in reality it should be 39.09 instead of 30.19

Let the abundance of 38.9367 g isotope be x% , the abundance of 39.9640 u isotope would be (100-x-6.73)% . Since the total abundance has to be equal to 100%

Thus:

(x*38.9367 + (100-x-6.73)39.9640 + 6.73 * 40.9618 )/100 = 39.09

38.9367x + 3996.40-39.9640x-268.95772+275.6729 =3909

1.027 x= 94.11

x= 91.635 %