Understanding the Chemistry

* Magnesium (Mg) forms a +2 ion (Mg²⁺).

* Chlorine (Cl) forms a -1 ion (Cl⁻).

Balancing the Charges

To form a neutral compound, we need two chloride ions (Cl⁻) for every one magnesium ion (Mg²⁺). This is because:

* 2 (Cl⁻) charges + 1 (Mg²⁺) charge = 0

Calculating the Moles

1. Mole Ratio: The mole ratio of Mg²⁺ to Cl⁻ is 1:2. This means for every 1 mole of Mg²⁺, we need 2 moles of Cl⁻.

2. Calculation: Since we have 0.25 moles of Mg²⁺, we need:

0.25 moles Mg²⁺ * (2 moles Cl⁻ / 1 mole Mg²⁺) = 0.50 moles Cl⁻

Answer: You need 0.50 moles of Cl⁻ ions to completely combine with 0.25 moles of Mg²⁺ ions.