Question

What is the average atomic mass of gold if half of the gold found in nature has a mass of 197 amu and half has a mass of 198 amu?

Answer 1

`"Average mass"=197.5a.m.u.`

Explanation:

The average atomic mass can be calculated by:

`"Average mass"=sum("isotope mass")xx("percent abundance")`

If half of gold is found in nature with a mass of `197a.m.u.` therefore its percent abundance is `50%` and the percent abundance of the isotope `""^198Au` is also `50%`.

`"Average mass"=(197xx(50%)/(100%))+(198xx(50%)/(100%))=197.5a.m.u.`