1. Determine the formula of aluminum chloride:

* Aluminum has a +3 charge (Al³⁺)

* Chloride has a -1 charge (Cl⁻)

* To balance the charges, the formula is AlCl₃

2. Calculate the molar mass of aluminum chloride:

* Al: 26.98 g/mol

* Cl: 35.45 g/mol

* Molar mass of AlCl₃ = 26.98 + (3 * 35.45) = 133.33 g/mol

3. Convert the mass of aluminum chloride to moles:

* Moles = mass / molar mass

* Moles of AlCl₃ = 0.2520 g / 133.33 g/mol = 0.00189 mol

4. Determine the mole ratio of chloride ions to aluminum chloride:

* From the formula AlCl₃, we see that there are 3 moles of Cl⁻ ions for every 1 mole of AlCl₃.

5. Calculate the moles of chloride ions:

* Moles of Cl⁻ = (moles of AlCl₃) * (mole ratio of Cl⁻/AlCl₃)

* Moles of Cl⁻ = 0.00189 mol * 3 = 0.00567 mol

Therefore, there are 0.00567 moles of chloride ions in 0.2520 g of aluminum chloride.