Question

A sample of carbon is 98% carbon-12 and 2% carbon-14. What is the average atomic mass of this mixture of isotope to the hundredths place?

Answer 1

`12.04 \ "amu"`

Explanation:

The average atomic mass of an atom with `"n"` isotopes is given by:

`("mass"_"isotope 1"*"abundance"_"isotope 1")+("mass"_"isotope 2"*"abundance"_"isotope 2")+...+("mass"_"isotope n"*"abundance"_"isotope n")`

And so, the average atomic mass of this sample would be:

`("mass"_(""^12C)*0.98)+("mass"_(""^14C)*0.02)`

`=12*0.98+14*0.02`

`=12.04`

Since atomic mass is measured in simple units, the mass of this sample is `12.04 \ "u"` or `12.04 \ "amu"`.