Question

The element gallium has an atomic mass of 69.7 u and consists of two stable isotopes gallium-69 and gallium-71. The isotope gallium-69 has a mass of 68.9 u and a percent natural abundance of 60.4 %. The isotope gallium-71 has a percent natural abundance of 39.6 %. What is the mass of gallium-71

Answer 1

70.9 u

Step-by-step explanation:

The average atomic mass (AM) of an element can be calculated using the following expression.

`AM=(\Sigma Ab\%_(i).m_(i) )/(100)`

where,

`Ab\%_(i)`: percent natural abundance of each isotope

`m_(i)`: mass of each isotope

Let x = mass of ⁷¹Ga. We get,

`69.7u=(60.4 * 68.9u + 39.6 * x )/(100) \\x = 70.9u`

Answer 2

70.92u

Step-by-step explanation:

The atomic mass expresed at fisrt (69.7u) is a combination of the atomic masses of both isotopes multiplied by their natural abundance. So we can describe "(68.9*.604)+(x*.396)=69.7" the as the equation neccesary to solve this problem, where x is the atomic mass of gallium-71. x=70.92.