Question

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

Answer 1

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.