Question

Potassium has three naturally occurring isotopes. According to one source of data, Potassium-39 (mass 38.9637 amu) makes up 93.26%, potassium-40 (mass 39.9640 amu) makes up just 0.01%, and potassium-41 (mass 40.9618 amu) makes up 6.73%. What is the average atomic mass of potassium based on these relative abundances

Answer 1

Answer:

Average atomic mass of potassium based on these relative abundances

$= 39.0944$

Explanation:

The atomic mass of this element will be equal to the sum of product of its three isotopic masses and its fractional abundance

For isotope I -

Mass of Potassium-39 $= 38.9637$ amu

Fractional abundance of Potassium-39 $= 93.26$ %

Mass of Potassium-40 $= 39.9640$ amu

Fractional abundance of Potassium-40 $= 0.01$ %

Mass of Potassium-41 $= 40.9618$ amu

Fractional abundance of Potassium-41 $= 6.73$%

Average atomic mass of potassium based on these relative abundances

$= (38.9636 * 0.9326)+ (39.9640*0.0001) + (40.9618 * 0.0673)\\= 36.3374 + 0.0003 + 2.7567\\= 39.0944$