In each of the following pairs, indicate which has the higher concentration of Cl^- ion: (a) 0.10 M AlCl₃ solution or a 0.25 M LiCl solution (b) 150 mL of a 0.05 M MnCl₃ solution or 200 mL of 0.10 M KCl solution (c) a 2.8 M HCl solution or a solution made by dissolving 23.5 g of KCl in water to make 100 mL of solution.

Verified step by step guidance

1. Step 1: For each solution, determine the number of moles of Cl⁻ ions produced per mole of compound. For example, AlCl₃ dissociates into one Al³⁺ ion and three Cl⁻ ions, so it produces 3 moles of Cl⁻ per mole of AlCl₃.
2. Step 2: Calculate the concentration of Cl⁻ ions for each solution by multiplying the molarity of the solution by the number of Cl⁻ ions produced per formula unit. For example, for a 0.10 M AlCl₃ solution, the concentration of Cl⁻ ions is 0.10 M × 3 = 0.30 M.
3. Step 3: For part (b), calculate the total moles of Cl⁻ ions in each solution by multiplying the volume (in liters) by the molarity and the number of Cl⁻ ions per formula unit. For example, for 150 mL of 0.05 M MnCl₃, convert the volume to liters and calculate the moles of Cl⁻.
4. Step 4: Compare the concentrations or total moles of Cl⁻ ions calculated in the previous steps for each pair of solutions to determine which has the higher concentration of Cl⁻ ions.
5. Step 5: For part (c), convert the mass of KCl to moles using its molar mass, then calculate the concentration of Cl⁻ ions in the solution by dividing the moles of Cl⁻ by the volume of the solution in liters. Compare this with the concentration of Cl⁻ ions in the 2.8 M HCl solution.

Key Concepts

Ionic Dissociation

Ionic dissociation refers to the process by which an ionic compound separates into its constituent ions when dissolved in a solvent, typically water. For example, when AlCl3 dissolves, it dissociates into one Al³⁺ ion and three Cl⁻ ions, resulting in a higher concentration of Cl⁻ ions compared to a compound that dissociates into fewer ions.

Molarity and Concentration

Molarity (M) is a measure of concentration defined as the number of moles of solute per liter of solution. It is crucial for comparing solutions, as higher molarity indicates a greater amount of solute in a given volume. Understanding how to calculate and compare molarity helps determine which solution has a higher concentration of specific ions.

Volume and Dilution Effects

The volume of a solution affects the total number of moles of solute present. When comparing solutions, it is important to consider both the concentration and the volume to find the total amount of a specific ion. For instance, a larger volume of a lower concentration solution may contain more total moles of an ion than a smaller volume of a higher concentration solution.