Calculate the atomic mass of gallium if gallium has 2 naturally occurring isotopes with the following masses and natural abundances: Ga-69 68.9256 amu 60.11%
Ga-71 70.9247 amu 39.89%
A) 69.72 amu
B) 69.93 amu
C) 70.00 amu
D) 69.80 amu
E) 70.68 amu

Question

Quizplus · Accepted Answer

The atomic mass of gallium is the weighted average of the masses of its isotopes, taking into account their natural abundances. The weighted average is calculated as follows:Atomic mass = (mass of isotope 1 x abundance of isotope 1) + (mass of isotope 2 x abundance of isotope 2)Atomic mass = (68.9256 amu x 0.6011) + (70.9247 amu x 0.3989)Atomic mass = 41.473 amu + 28.251 amuAtomic mass = 69.724 amuTherefore, the atomic mass of gallium is 69.72 amu, which is closest to choice A, 69.72 amu.

Calculate the Atomic Mass of Gallium If Gallium Has 2