Question

Gallium has two naturally occurring isotopes. 69Ga (68.9257 amu) is the more abundant isotope, at 60.400%. If the atomic mass of gallium is 69.723 amu, what is the mass of the other isotope, 71Ga

Answer 1

70.9391 amu

Step-by-step explanation:

The abundance of the second isotope is 100 - 60.4% = 39.6%.

We can solve this problem by keeping in mind the following formula for atomic mass:

• Atomic mass = Mass of Isotope 1 * Abundance + Mass of Isotope 2 * Abundance

We input the given data:

• 69.723 = 68.9257 * 60.4/100 + Mass of Isotope 2 * 39.6/100

• Mass of Isotope 2 = 70.9391 amu