Textbook Question
Potassium nitrate has a lattice energy of -163.8 kcal/mol and a heat of hydration of -155.5 kcal/mol. How much potassium nitrate has to dissolve in water to absorb 1.00⨉102 kJ of heat?
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Ch.14 - Solutions
Tro5th EditionChemistry: A Molecular ApproachISBN: 9780134874371
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Table of contents
- Ch.1 - Matter, Measurement & Problem Solving93
- Ch.2 - Atoms & Elements94
- Ch.3 - Molecules and Compounds103
- Ch.4 - Chemical Reactions and Chemical Quantities44
- Ch.5 - Introduction to Solutions and Aqueous Solutions69
- Ch.6 - Gases97
- Ch.7 - Thermochemistry85
- Ch.8 - The Quantum-Mechanical Model of the Atom48
- Ch.9 - Periodic Properties of the Elements73
- Ch.10 - Chemical Bonding I: The Lewis Model76
- Ch.11 - Chemical Bonding II: Molecular Shapes, VSEPR & MO Theory70
- Ch.12 - Liquids, Solids & Intermolecular Forces41
- Ch.13 - Solids & Modern Materials40
- Ch.14 - Solutions76
- Ch.15 - Chemical Kinetics90
- Ch.16 - Chemical Equilibrium56
- Ch.17 - Acids and Bases121
- Ch.18 - Aqueous Ionic Equilibrium127
- Ch.19 - Free Energy & Thermodynamics78
- Ch.20 - Electrochemistry87
- Ch.21 - Radioactivity & Nuclear Chemistry60
- Ch.22 - Organic Chemistry115
Chapter 14, Problem 42
A solution contains 32 g of KNO3 per 100.0 g of water at 25 °C. Is the solution unsaturated, saturated, or supersaturated? (Use Figure 13.11.)
Verified step by step guidance1
Determine the solubility of KNO3 in water at 25 °C from Figure 13.11 or a similar solubility chart.
Calculate the mass of KNO3 that can be dissolved in 100.0 g of water at 25 °C using the solubility data.
Compare the actual mass of KNO3 in the solution (32 g) to the calculated mass from step 2.
If the actual mass is less than the calculated mass, the solution is unsaturated. If it is equal, the solution is saturated. If it is more, the solution is supersaturated.
Conclude whether the solution is unsaturated, saturated, or supersaturated based on the comparison.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Solubility
Solubility is the maximum amount of a solute that can dissolve in a given amount of solvent at a specific temperature. For KNO3 in water at 25 °C, solubility is a critical factor in determining whether a solution is unsaturated, saturated, or supersaturated. Understanding solubility helps predict how much solute can be dissolved before reaching a limit.
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Solubility Rules
Saturated Solution
A saturated solution is one in which the maximum amount of solute has been dissolved in the solvent at a given temperature. At this point, any additional solute will not dissolve and will remain as a solid. Identifying whether a solution is saturated involves comparing the amount of solute present to the solubility limit at the specified temperature.
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Supersaturation
Supersaturation occurs when a solution contains more solute than it can theoretically hold at a given temperature, often achieved by heating the solution and then cooling it slowly. This state is unstable, and any disturbance can cause the excess solute to precipitate out. Recognizing supersaturation is essential for understanding the behavior of solutions under varying conditions.
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Related Practice
Textbook Question
Use the data to calculate the heats of hydration of lithium chloride and sodium chloride. Which of the two cations, lithium or sodium, has stronger ion–dipole interactions with water? Why?
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Textbook Question
A KCl solution containing 42 g of KCl per 100.0 g of water is cooled from 60 °C to 0 °C. What happens during cooling? (Use Figure 14.11.)