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Ch.4 - Reactions in Aqueous Solution
Chapter 4, Problem 72b

Indicate the concentration of each ion present in the solution formed by mixing: (b) 44.0 mL of 0.100 M Na2SO4 with 25.0 mL of 0.150 M KCl

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1
Calculate the moles of Na<sub>2</sub>SO<sub>4</sub> by using the formula: moles = molarity × volume in liters. Convert the volume from mL to liters by dividing by 1000.
Calculate the moles of KCl using the same method as in step 1.
Recognize that Na<sub>2</sub>SO<sub>4</sub> dissociates into 2 Na<sup>+</sup> ions and 1 SO<sub>4</sub><sup>2-</sup> ion. Multiply the moles of Na<sub>2</sub>SO<sub>4</sub> by 2 to find the moles of Na<sup>+</sup> ions, and use the original moles of Na<sub>2</sub>SO<sub>4</sub> for the moles of SO<sub>4</sub><sup>2-</sup> ions.
Recognize that KCl dissociates into K<sup>+</sup> and Cl<sup>-</sup> ions. The moles of KCl will be equal to the moles of K<sup>+</sup> and Cl<sup>-</sup> ions.
Calculate the total volume of the solution by adding the volumes of the Na<sub>2</sub>SO<sub>4</sub> and KCl solutions. Convert this total volume to liters. Use this volume to calculate the concentration of each ion by dividing the moles of each ion by the total volume in liters.

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Key Concepts

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

Molarity

Molarity (M) is a measure of concentration defined as the number of moles of solute per liter of solution. It is crucial for calculating the concentration of ions in a solution after mixing different solutions. To find the final concentration of ions, one must consider the volume and molarity of each solution before mixing.
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Stoichiometry

Stoichiometry involves the calculation of reactants and products in chemical reactions. In this context, it helps determine the number of moles of each ion produced when two solutions are mixed. Understanding the stoichiometric relationships allows for accurate calculations of ion concentrations in the resulting solution.
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Dilution

Dilution refers to the process of reducing the concentration of a solute in a solution, typically by adding more solvent. When two solutions are mixed, the total volume increases, which affects the concentration of each ion. The dilution equation (C1V1 = C2V2) can be applied to find the new concentrations of ions after mixing.
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