# The atomic weight of Ga is 69.72 amu. There are only two naturally occurring isotopes of gallium: "^69Ga with a weight of 69.0 amu, and "^71Ga with a weight of 71.0 amu. What is approximate natural abundance of the "^71Ga isotope?

Jun 6, 2017

The natural abundance is =36%

#### Explanation:

Let the percentage of the isotope ""^71Ga be =x%

Then,

The percentage of the isotope ""^69Ga is =(100-x)%

We write the mass balance equation

$100 \cdot 69.72 = x \cdot 71 + \left(100 - x\right) \cdot 69$

$6972 = 71 x + 6900 - 69 x$

$2 x = 6972 - 6900 = 72$

$x = 36$

Therefore,

The percentage of the isotope ""^71Ga is =36%