8. How many atoms of cobalt are in a 0.39 mole sample of CoC

8.98

*

N

A

cobalt atoms

Explanation:

N

A

,

Avogadro's number

specifies

6.0221

*

10

23

individual particles. It is simply another collective number like a dozen, or a score, or a gross.

N

A

has the property that

6.0221

*

10

23

individual cobalt atoms has a mass of

58.93

⋅

g

. How did I know that? Did I have it memorized?

So the quantity is

≈

54

*

10

23

cobalt atoms.