How many moles (of molecules or formula units) are in each sample? 79.34 g cf2cl2?

From the periodic table:

molecular mass of carbon = 12 grams

molecular mass of fluorine = 18.99 grams

molecular mass of chlorine = 35.5 grams

Therefore:

one mole of CF2Cl2 = 12 + 2 (18.99) + 2 (35.5) = 120.98 grams

Therefore, we can use cross multiplication to find the number of moles in 79.34 grams as follows:

mass = (79.34 x 1) / 120.98 = 0.6558 moles

Now, one mole contains 6.022 x 10^23 molecules, therefore:

number of molecules in 0.65548 moles = 0.6558 x 6.022 x 10^23

= 3.949 x 10^23 molecules