The Ions present in CaCl₂ are,
Ca²⁺ Cl⁻ Cl⁻
Means 1 formula unit contains 1 Ca²⁺ ion and 2 Cl⁻ ions.
Also, 1 mole of CaCl₂ contains 6.022 × 10²³ formula units.
So, 1 mole formula units of CaCl₂ contain,
2 × 6.022 × 10²³ = 1.20 × 10²⁴ Cl⁻ Ions
Now, Calculating number of moles contained by 220 g of CaCl₂,
As,
110.98 g of CaCl₂ = 1 mole
Then,
220 g of CaCl₂ = X moles
Solving for X,
X = (220 g × 1 mol) ÷ 110.98 g
X = 1.98 moles
As,
1 mole contained = 1.20 × 10²⁴ Cl⁻ Ions
Then,
1.98 mole will contain = X Cl⁻ Ions
Solving for X,
X = (1.98 mol × 1.20 × 10²⁴ Ions) ÷ 1mol
X = 2.38 × 10²⁴ Cl⁻ Ions