Which of the following solutions will have the highest concentration of chloride ions?

• A. 0.40 M MgCl2
• B. 0.20 M LiCl
• C. 0.60 M AlCl3
• D. 0.40 M CaCl2

Answer: (C)

Verified step by step guidance

1. Identify the chemical formula for each compound to determine the number of chloride ions produced per formula unit. MgCl2, LiCl, AlCl3, and CaCl2 are the compounds in question.
2. Understand that the concentration given is for the entire compound, not just the chloride ions. Therefore, you need to consider the dissociation of each compound in water.
3. For each compound, determine the number of chloride ions produced per mole of compound. MgCl2 dissociates into one Mg²⁺ ion and two Cl⁻ ions, LiCl dissociates into one Li⁺ ion and one Cl⁻ ion, AlCl3 dissociates into one Al³⁺ ion and three Cl⁻ ions, and CaCl2 dissociates into one Ca²⁺ ion and two Cl⁻ ions.
4. Calculate the concentration of chloride ions for each solution by multiplying the molarity of the compound by the number of chloride ions produced per formula unit. Use the formula: \( \text{[Cl}^-\text{]} = \text{Molarity of compound} \times \text{Number of Cl}^- \text{ ions per formula unit} \).
5. Compare the calculated concentrations of chloride ions for each solution to determine which has the highest concentration.