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Ch.4 - Reactions in Aqueous Solution
Chapter 4, Problem 79c

Predict whether a precipitation reaction will occur when aqueous solutions of the following substances are mixed. For those that form a precipitate, write the net ionic reaction. (c)

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Identify the ions present in each of the aqueous solutions. For example, if you have solutions of NaCl and AgNO_3, the ions present are Na^+, Cl^-, Ag^+, and NO_3^-.
Determine the possible combinations of cations and anions that can form new compounds. In our example, the possible combinations are NaNO_3 and AgCl.
Use the solubility rules to determine if any of the new combinations form an insoluble compound (precipitate). According to the solubility rules, most chloride salts are soluble, except for those of Ag^+, Pb^2+, and Hg_2^2+. Therefore, AgCl is insoluble and will precipitate.
Write the balanced molecular equation for the reaction, showing the reactants and the products, including the precipitate. For example: NaCl(aq) + AgNO_3(aq) → NaNO_3(aq) + AgCl(s).
Write the net ionic equation by removing the spectator ions (ions that do not participate in the formation of the precipitate) from the complete ionic equation. For the example, the net ionic equation is: Ag^+(aq) + Cl^-(aq) → AgCl(s).

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Key Concepts

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

Precipitation Reactions

Precipitation reactions occur when two aqueous solutions are mixed, resulting in the formation of an insoluble solid, known as a precipitate. This happens when the product of the reaction has a solubility product (Ksp) that is exceeded in the solution, leading to the aggregation of ions into a solid form. Understanding the solubility rules helps predict whether a precipitate will form.
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Solubility Rules

Solubility rules are guidelines that help predict the solubility of various ionic compounds in water. These rules indicate which combinations of cations and anions will form soluble or insoluble compounds. For example, most nitrates are soluble, while many carbonates are not. Familiarity with these rules is essential for determining the outcome of mixing different ionic solutions.
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Net Ionic Equations

A net ionic equation represents the actual chemical species that participate in a reaction, omitting the spectator ions that do not change during the reaction. This equation highlights the formation of the precipitate and provides a clearer picture of the chemical changes occurring. Writing net ionic equations is crucial for accurately depicting precipitation reactions and understanding the underlying chemistry.
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