How many moles of carbon are in 7.87*10^7

Well one mole of stuff, any stuff, including carbon dioxide, specifies

6.022

*

10

23

individual items of that stuff.

Explanation:

And thus we work out the quotient:

7.2

*

10

25

⋅

carbon dioxide molecules

6.022

*

10

23

⋅

carbon dioxide molecules

⋅

m

o

l

-

1

≅

120

⋅

m

o

l

carbon dioxide

.

This is dimensionally consistent, because we get an answer with units

1

m

o

l

-

1

=

1

1

mol

=

m

o

l

as required.