1. Identify the elements and their atomic masses:

* Cu (Copper): Atomic mass = 63.55 amu

* Cl (Chlorine): Atomic mass = 35.45 amu

2. Determine the number of atoms of each element in the formula:

* CuCl₂ has 1 copper atom (Cu) and 2 chlorine atoms (Cl).

3. Calculate the formula mass:

* (1 Cu atom * 63.55 amu/Cu atom) + (2 Cl atoms * 35.45 amu/Cl atom) =

* 63.55 amu + 70.90 amu =

* 134.45 amu

Therefore, the formula mass of CuCl₂ is 134.45 amu.