.
Step-by-step explanation
Refer to a modern periodic table for relative atomic mass:
Formula of copper (II) chloride: CuCl₂.
Formula mass of copper (II) chloride:
63.546 + 2 × 35.45 =
.
How many
of formula units in 8.3 grams of CuCl₂?

Note the subscript "2" in the formula CuCl₂. There are
of chloride ions in every
formula unit of CuCl₂.
There would be
of
ions in
formula units of CuCl₂.
The mass of
of chloride ion is 35.45 grams.
The mass of
of
ions will be
.
Round the final value to two sig. fig. since the mass in the question is also 2 sig. fig.