Mole of Chloride ions ?

Mass fraction of Cl⁻ ions in CuCl₂ = 35.5×2/(63.5 + 35.5×2) = 71.0/134.5

Mass of Cl⁻ ions in 8.3 g of CuCl₂ = 8.3 × (71.0/134.5) g = 4.4 g
(to 2 sig. fig.)