Question

You have 4.72x10^25 atoms of a substance with MW of 136.94 g/mol How many moles do you have

Answer 1

Number of moles = 78.41

Further explanation  

The mole is the number of particles(molecules, atoms, ions) contained in a substance  

1 mol = 6.02.10²³ particles

Can be formulated

N=n x No

N = number of particles

n = mol

No = Avogadro's = 6.02.10²³

4.72 x 10²⁵ atoms of a substance, then moles :

$\tt n=\dfrac{N}{No}\\\\n=\dfrac{4.72\times 10^{25}}{6.02\times 10^{23}}\\\\n=78.41$