Question

How many moles are found in a 100.0 g sample of CuF2?

Answer 1

You can solve this by dividing the mass by the molar mass. The molar mass of CuF2 is about 101.5 g/mol. Therefore there are 100.0/101.5 = 0.985 mol.

Answer 2

The molar mass is calculated by the sum of the mass numbers of the atoms that form the molecule. For example: CuF2
Cu: 1*63,54u = 63,54u 
F: 2*19u = 38u
Thus, the molar mass of CuF2 is: 63,54+38= 101,54 g/ mol.
And the number of mol is calculated by the mass divided by the molar mass or it can be solving through the rule of 3. For example:

100 g de CuF2
101,54 g → 1 mol
100 g  → x

101,54x = 100
x = 100/101,54
x = 0,98483... → $\boxed{x \approx 0,985 mol}$

I hope I have helped you, good studies!