Gallium has an atomic mass of 69.723 amu. The abundance of Ga-69 (68.926 amu)is 60.11%. What is the atomic mass, in amu, of the other isotope?
A)70.924 amu
B)70.928 amu
C)70.932 amu
D)70.920 amu
E)70.930 amu

Question

Quizplus · Accepted Answer

The atomic mass of gallium is the weighted average of its isotopes. Using the formula: (68.926 * 0.6011) + (x * 0.3989) = 69.723, solving for x gives approximately 70.924 amu.

Gallium Has an Atomic Mass of 69