Question

A hypothetical pure element consists entirely

of two isotopes. The natural percent abun-
dance of the isotope with mass 25.9 u is 39.1%.
The other isotope has mass 30 u. Calculate
the atomic weight of the naturally occurring
element.

Answer 1

The atomic weight of the naturally occurring element can be calculated by taking the weighted average of its isotopes.

Step-by-step explanation:

The atomic weight of the naturally occurring element can be calculated by taking the weighted average of its isotopes. In this case, the element consists of two isotopes, one with a mass of 25.9 u and a natural abundance of 39.1%, and the other with a mass of 30 u.

To calculate the atomic weight, we need to multiply the mass of each isotope by its abundance, and then sum up these values.

For the first isotope: (25.9 u)(0.391) = 10.13 u

For the second isotope: (30 u)(1-0.391) = 17.73 u

Adding these values together, we get a total of 27.86 u as the atomic weight of the naturally occurring element.