An aqueous solution contains 1.2 mM of total ions. (b) If the solution is FeCl3(aq), what is the concentration of chloride ion?

Verified step by step guidance

1. Identify the dissociation equation for FeCl_3 in water: FeCl_3(aq) \rightarrow Fe^{3+}(aq) + 3Cl^{-}(aq).
2. Recognize that for every 1 mole of FeCl_3 that dissociates, 3 moles of Cl^- ions are produced.
3. Given that the total concentration of ions is 1.2 mM, determine the concentration of FeCl_3 by considering the stoichiometry of the dissociation.
4. Calculate the concentration of Cl^- ions by multiplying the concentration of FeCl_3 by 3, as each FeCl_3 produces 3 Cl^- ions.
5. Express the concentration of Cl^- ions in mM, ensuring the units are consistent with the given total ion concentration.

Key Concepts

Dissociation of Ionic Compounds

Ionic compounds, such as FeCl3, dissociate into their constituent ions when dissolved in water. For FeCl3, it separates into one Fe³⁺ ion and three Cl⁻ ions. Understanding this dissociation is crucial for calculating the concentration of individual ions in a solution.

Molarity and Concentration

Molarity (M) is a measure of concentration defined as the number of moles of solute per liter of solution. In this case, the total ion concentration is given in millimoles per liter (mM), which can be converted to moles per liter. This concept is essential for determining the concentration of specific ions in the solution.

Stoichiometry in Solutions

Stoichiometry involves the quantitative relationships between reactants and products in a chemical reaction. In the context of this question, it helps to determine the ratio of ions produced from the dissociation of FeCl3, allowing us to calculate the concentration of chloride ions based on the total ion concentration.