Question

How many moles are equal to `1.2 times 10^21` molecules of lithium?

Answer 1

`1.2xx10^21color(white)(.)"atoms Li"=2.0xx10^(-3)color(white)(.)"mol Li"`.

Explanation:

Lithium is a metal. It does not exist as molecules. We can, however, determine the moles equal to `1.2xx10^21` atoms of lithium.

`"1 mol atoms"=6.022xx10^23` atoms

`1.2xx10^21color(red)cancel(color(black)("atoms Li"))xx(1"mol Li atoms")/(6.022xx10^23color(red)cancel(color(black)("atoms Li")))=2.0xx10^(-3)"mol Li"` (rounded to two significant figures)