Answer:
1.31×10^-16moles
Explanation:
If 1 mole of carbon contains 6.02×10^23 carbon atoms (Avogadro's number)
X moles of carbon contain 7.87×10^7 carbon atoms
X = 7.87×10^7/6.02×10^23
X= 1.31×10^-16moles
Note that 1 moles of any substance contains Avogadro's number of elementary entities (atoms, ions, molecules etc)
