Textbook Question
A solution containing sodium fluoride is mixed with one containing calcium nitrate to form a solution that is 0.015 M in NaF and 0.010 M in Ca(NO3)2. Does a precipitate form in the mixed solution? If so, identify the precipitate.
Ch.17 - Aqueous Ionic Equilibrium
Tro4th EditionChemistry: A Molecular ApproachISBN: 9780134112831
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Table of contents
- Ch.1 - Matter, Measurement & Problem Solving136
- Ch.2 - Atoms & Elements112
- Ch.3 - Molecules, Compounds & Chemical Equations159
- Ch.4 - Chemical Quantities & Aqueous Reactions140
- Ch.5 - Gases118
- Ch.6 - Thermochemistry106
- Ch.7 - Quantum-Mechanical Model of the Atom62
- Ch.8 - Periodic Properties of the Elements103
- Ch.9 - Chemical Bonding I: The Lewis Model104
- Ch.10 - Chemical Bonding II: Molecular Shapes & Valence Bond Theory89
- Ch.11 - Liquids, Solids & Intermolecular Forces73
- Ch.12 - Solids and Modern Material59
- Ch.13 - Solutions110
- Ch.14 - Chemical Kinetics140
- Ch.15 - Chemical Equilibrium78
- Ch.16 - Acids and Bases155
- Ch.17 - Aqueous Ionic Equilibrium176
- Ch.18 - Free Energy and Thermodynamics108
- Ch.19 - Electrochemistry118
- Ch.20 - Radioactivity and Nuclear Chemistry82
- Ch.21 - Organic Chemistry150
Chapter 17, Problem 103
Predict whether a precipitate will form if you mix 75.0 mL of a NaOH solution with pOH = 2.58 with 125.0 mL of a 0.018 M MgCl2 solution. Identify the precipitate, if any.
Verified step by step guidance1
Calculate the concentration of OH⁻ ions in the NaOH solution using the pOH value: \[ \text{[OH}^-\text{]} = 10^{-\text{pOH}} \].
Determine the moles of OH⁻ ions in the 75.0 mL NaOH solution by multiplying the concentration of OH⁻ by the volume in liters.
Calculate the moles of Mg²⁺ ions in the 125.0 mL MgCl₂ solution using the concentration and volume.
Determine the final concentrations of OH⁻ and Mg²⁺ ions after mixing by dividing the moles of each ion by the total volume of the mixed solution.
Use the solubility product constant (Ksp) for Mg(OH)₂ to determine if the product of the ion concentrations \([\text{Mg}^{2+}][\text{OH}^-]^2\) exceeds the Ksp, indicating a precipitate will form.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
pOH and pH Relationship
pOH is a measure of the hydroxide ion concentration in a solution, and it is related to pH by the equation pH + pOH = 14. A pOH of 2.58 indicates a high concentration of hydroxide ions, which can influence the solubility of certain metal hydroxides, such as magnesium hydroxide.
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Solubility Product Constant (Ksp)
The solubility product constant (Ksp) is an equilibrium constant that describes the solubility of a sparingly soluble ionic compound. For magnesium hydroxide (Mg(OH)2), the Ksp value helps determine whether a precipitate will form when magnesium ions from MgCl2 react with hydroxide ions from NaOH.
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Precipitation Reactions
Precipitation reactions occur when two soluble salts react in solution to form an insoluble compound, or precipitate. In this case, mixing NaOH and MgCl2 can lead to the formation of magnesium hydroxide, which is insoluble in water, thus resulting in a precipitate if the product of the ion concentrations exceeds the Ksp.
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Related Practice
Textbook Question
Determine the minimum concentration of the precipitating agent on the right to cause precipitation of the cation from the solution on the left. a. 0.035 M Ba(NO3)2; NaF
Textbook Question
Determine if each compound is more soluble in acidic solution than it is in pure water. Explain. a. Hg2Br2 b. Mg(OH)2 c. CaCO3 d. AgI