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Ch.4 - Reactions in Aqueous Solution
Chapter 4, Problem 24b

Identify the precipitate (if any) that forms when the following solutions are mixed, and write a balanced equation for each reaction. b. KOH and Cu(NO3)2



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Identify the ions present in each solution: KOH dissociates into K^+ and OH^- ions, while Cu(NO_3)_2 dissociates into Cu^{2+} and NO_3^- ions.
Determine the possible combinations of cations and anions that can form new compounds: K^+ with NO_3^- and Cu^{2+} with OH^-.
Use solubility rules to determine which of these combinations, if any, will form a precipitate: KNO_3 is soluble, while Cu(OH)_2 is insoluble.
Write the balanced chemical equation for the reaction, showing the formation of the precipitate: Cu(OH)_2(s) is the precipitate formed.
Balance the equation by ensuring the number of atoms of each element is the same on both sides of the equation.

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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 soluble salts react in solution to form an insoluble product, known as a precipitate. This process is driven by the formation of a compound that cannot remain dissolved in the solvent, leading to the separation of solid material from the liquid. Understanding solubility rules helps predict whether a precipitate will form when two solutions are mixed.
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Solubility Rules

Solubility rules are guidelines that help predict the solubility of various ionic compounds in water. For example, most hydroxides are insoluble except for those of alkali metals and some alkaline earth metals. In the case of KOH and Cu(NO3)2, knowing these rules allows us to determine that Cu(OH)2 will precipitate when these two solutions are mixed.
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Balanced Chemical Equations

A balanced chemical equation represents a chemical reaction with equal numbers of each type of atom on both sides of the equation. Balancing ensures the law of conservation of mass is upheld, meaning that matter is neither created nor destroyed in the reaction. For the reaction between KOH and Cu(NO3)2, the balanced equation will show the formation of Cu(OH)2 as a precipitate along with the remaining soluble products.
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