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Ch.5 - Introduction to Solutions and Aqueous Solutions
Chapter 5, Problem 9

We prepare a solution by mixing 0.10 L of 0.12 M sodium chloride with 0.23 L of a 0.18 M MgCl2 solution. What volume of a 0.20 M silver nitrate solution is needed to precipitate all the Cl- ions in the solution as AgCl?

Verified step by step guidance
1
Calculate the moles of Cl- ions from the NaCl solution using the formula: \( \text{moles} = \text{volume} \times \text{molarity} \).
Calculate the moles of Cl- ions from the MgCl2 solution. Remember that each mole of MgCl2 provides 2 moles of Cl- ions.
Add the moles of Cl- ions from both solutions to find the total moles of Cl- ions present.
Use the stoichiometry of the reaction between Cl- ions and Ag+ ions to determine the moles of Ag+ needed. The reaction is: \( \text{Ag}^+ + \text{Cl}^- \rightarrow \text{AgCl} \).
Calculate the volume of 0.20 M AgNO3 solution required to provide the necessary moles of Ag+ ions using the formula: \( \text{volume} = \frac{\text{moles}}{\text{molarity}} \).

Key Concepts

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

Molarity (M)

Molarity is a measure of concentration defined as the number of moles of solute per liter of solution. It is expressed in moles per liter (mol/L). Understanding molarity is crucial for calculating the amount of reactants needed in a chemical reaction, as it allows for the conversion between volume and moles.
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Precipitation Reaction

A precipitation reaction occurs when two soluble salts react in solution to form an insoluble salt, known as a precipitate. In this case, silver nitrate reacts with chloride ions to form silver chloride (AgCl), which is insoluble in water. Recognizing the reactants and products in such reactions is essential for determining the stoichiometry involved.
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Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions based on the balanced chemical equation. It involves using mole ratios derived from the coefficients of the balanced equation to determine how much of each substance is needed or produced. This concept is vital for solving the problem, as it allows for the calculation of the volume of silver nitrate required to fully react with the chloride ions.
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