Question

Naturally occurring gallium consists of two isotopes: Ga-69 and Ga-71 with relative abundances of 60% and 40% respectively. If their masses are 68.93 amu and 70.92 amu, what is the average atomic mass of gallium?

a) 69.93 amu
b) 69.72 amu
c) 69.37 amu
d) 69.00 amu

Answer 1

The average atomic mass of gallium is 69.72 amu

Step-by-step explanation:

The average atomic mass of an element is calculated by multiplying the mass of each isotope by its relative abundance, and then summing up the products. In this case, we have two isotopes of gallium: Ga-69 and Ga-71, with relative abundances of 60% and 40%, and masses of 68.93 amu and 70.92 amu, respectively. To calculate the average atomic mass, we can use the formula:

Average atomic mass = (mass of Ga-69 * abundance of Ga-69) + (mass of Ga-71 * abundance of Ga-71)

Plugging in the values:

Average atomic mass = (68.93 amu * 0.60) + (70.92 amu * 0.40) = 41.358 amu + 28.368 amu = 69.726 amu

So the average atomic mass of gallium is approximately 69.72 amu.