The molar mass of copper(ii) chloride (cucl2) is 134.45 g/mol. how many formula units of cucl2 are present in 17.6 g of cucl2?
a. 7.88 × 10^22 formula units
b. 1.84 × 10^23 formula units
c. 1.91 × 10^23 formula units
d. 1.42 × 1024 formula units

You just need to divide the total mass of the compound (CuCl2) by its molar mass (given the the molar mass is the mass of one mole of compound) to find the number of moles. After that, convert the number of moles in number of units.

So,  17.6 g / 134.45 g/mol = 0.1309 moles.

And now use Avogadro's number to convert to number of units:

 => 0.1309 moles * (6.02 * 10^23 units / mol) =0.788*10^ 23 units = 7.88*10^22 units

option A) 7.88 * 10^ 22 units.