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Ch.4 - Reactions in Aqueous Solution
All textbooksBrown 14th EditionCh.4 - Reactions in Aqueous SolutionProblem 23
Chapter 4, Problem 23

Will precipitation occur when the following solutions are mixed? If so, write a balanced chemical equation for the reaction. (a) Ca(CH3COO)2 and NaOH (b) K2CO3 and NH4NO3, (c) Na2S and FeCl3.

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1
Identify the ions present in each solution: Na2S dissociates into 2 Na^+ and S^2- ions, while FeCl3 dissociates into Fe^3+ and 3 Cl^- ions.
Determine the possible combinations of cations and anions that could form a precipitate: Fe^3+ can combine with S^2- to potentially form Fe2S3.
Use the solubility rules to determine if Fe2S3 is insoluble in water. According to the rules, most sulfides (S^2-) are insoluble except those of alkali metals and alkaline earth metals.
Since Fe2S3 is insoluble, a precipitation reaction will occur. Write the balanced chemical equation for the reaction: 2 FeCl3(aq) + 3 Na2S(aq) -> Fe2S3(s) + 6 NaCl(aq).
Verify that the equation is balanced by checking that the number of each type of atom 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 are mixed, resulting in the formation of an insoluble compound, or precipitate. This process is driven by the low solubility of the product in the solution, leading to its separation from the liquid phase. Understanding the solubility rules helps predict whether a precipitate will form when specific ionic compounds are combined.
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Solubility Rules

Solubility rules are guidelines that help predict the solubility of various ionic compounds in water. For example, most sulfides (like Na2S) are insoluble except for those of alkali metals and ammonium. Knowing these rules allows chemists to determine which combinations of ions will result in a precipitate when mixed in solution.
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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. Writing a balanced equation for a precipitation reaction involves identifying the reactants, the products formed, and ensuring that the number of atoms for each element is the same on both sides.
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Related Practice
Textbook Question

Acetone, CH3COCH3, is a nonelectrolyte; hypochlorous acid, HClO, is a weak electrolyte; and ammonium chloride, NH4Cl, is a strong electrolyte. (b) If 0.1 mol of each compound is dissolved in solution, which one contains 0.2 mol of solute particles, which contains 0.1 mol of solute particles, and which contains somewhere between 0.1 and 0.2 mol of solute particles?

Textbook Question

Using solubility guidelines, predict whether each of the following compounds is soluble or insoluble in water: (a) MgBr2 (b) NH4OH (c) Ni(CH3COO)2 (d) AgNO3 (e) FeCO3.

Textbook Question

Predict whether each of the following compounds is soluble in water: (a) MgS (b) Cr(OH)3 (c) ZnCl2 (d) Pb3(PO4)2 (e) Sr(CH3COO)2.

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Textbook Question

Identify the precipitate (if any) that forms when the following solutions are mixed, and write a balanced equation for each reaction. (a) NH4I and CuCl2 (b) LiOH and MnCl2 (c) K3PO4 and CoSO4

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Textbook Question

Which ions remain in solution, unreacted, after each of the following pairs of solutions is mixed? (a) potassium carbonate and magnesium sulfate

Textbook Question

Which ions remain in solution, unreacted, after each of the following pairs of solutions is mixed? (c) ammonium phosphate and calcium chloride