If 1.00 g of an unknown molecular compound contains 8.35  1021 molecules, what is its molar mass?

Answer is: molar mass of molecular compound is 71,95 g/mol.
N(compound) = 8,35·10²¹.
n(compound) = N(compound) ÷ Na.
n(compound) = 8,35·10²¹ ÷ 6,022·10²³ 1/mol.
n(compound) = 0,0139 mol.
m(compound) = 1,00 g.
M(compound) = m(compound) ÷ n(compound).
M(compound) = 1 g ÷ 0,0139 mol.
M(compound) = 71,95 g/mol.

Exothermic,  physical change after it is already baked