To find out how many moles is 1.5x10^23 atoms of Carbon, we will use Avogadro's number, which is represented by 6.022x10^23 atoms or molecules per mol.
To convert from atoms to moles, divide the atoms by Avogadro's number.
So, now we can convert the numbers into proper form:
1.5x10^23 ---> 1.5E23
6.022x10^23 ---> 6.022E23
Then, we divide them.
1.5E23/6.022E23 = 0.24908
Round to nearest hundredth.
0.24908 --> 0.25
Therefore, there are 0.25 moles of carbon in 1.5E23 atoms of carbon.