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Ch.5 - Introduction to Solutions and Aqueous Solutions
Chapter 5, Problem 26c

What is the molarity of Br- in each solution? 0.200 m AlBr3

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1
Identify the chemical formula of the compound: AlBr_3.
Determine the number of bromide ions (Br^-) produced per formula unit of AlBr_3. Since AlBr_3 dissociates into one Al^3+ ion and three Br^- ions, there are 3 moles of Br^- for every mole of AlBr_3.
Use the given molality of AlBr_3, which is 0.200 m, to find the molarity of Br^-. Since molality is moles of solute per kilogram of solvent, and assuming the density of the solution is close to that of water, molality can be approximated to molarity for dilute solutions.
Calculate the molarity of Br^- by multiplying the molality of AlBr_3 by the number of Br^- ions produced per formula unit: 0.200 m * 3.
Express the final molarity of Br^- in the solution.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Molarity

Molarity is a measure of concentration defined as the number of moles of solute per liter of solution. It is expressed in units of moles per liter (mol/L). Understanding molarity is essential for calculating the concentration of ions in a solution, which is crucial for various chemical reactions and processes.
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Dissociation of Ionic Compounds

Ionic compounds, such as aluminum bromide (AlBr3), dissociate into their constituent ions when dissolved in water. For AlBr3, it dissociates into one aluminum ion (Al^3+) and three bromide ions (Br^-). This dissociation is important for determining the concentration of specific ions in solution, such as Br^- in this case.
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Stoichiometry of Dissociation

Stoichiometry involves the quantitative relationships between reactants and products in a chemical reaction. In the context of dissociation, it helps to determine the number of moles of each ion produced from a given amount of the ionic compound. For AlBr3, the stoichiometry indicates that one mole of AlBr3 produces three moles of Br^-, which is crucial for calculating the molarity of Br^- in the solution.
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