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Ch.13 - Solutions & Their Properties
All textbooksMcMurry 8th EditionCh.13 - Solutions & Their PropertiesProblem 37
Chapter 13, Problem 37

Why do ionic substances with higher lattice energies tend to be less soluble in water than substances with lower lattice energies?

Verified step by step guidance
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Step 1: Understand the concept of lattice energy. Lattice energy is the energy required to separate one mole of an ionic solid into its gaseous ions. It is a measure of the strength of the forces holding the ions together in the solid.
Step 2: Recognize the relationship between lattice energy and solubility. Solubility of an ionic compound in water depends on the balance between lattice energy and the hydration energy (the energy released when ions interact with water molecules).
Step 3: Analyze the effect of high lattice energy. When an ionic compound has a high lattice energy, it means that a large amount of energy is required to break the ionic bonds in the solid. This makes it more difficult for the compound to dissolve in water.
Step 4: Consider the role of hydration energy. For an ionic compound to dissolve, the hydration energy must be sufficient to overcome the lattice energy. If the lattice energy is much higher than the hydration energy, the compound will be less soluble.
Step 5: Conclude the relationship. Ionic substances with higher lattice energies tend to be less soluble in water because the energy required to break the ionic bonds is not sufficiently compensated by the energy released during hydration, making dissolution energetically unfavorable.

Key Concepts

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

Lattice Energy

Lattice energy is the amount of energy released when gaseous ions combine to form an ionic solid. It is a measure of the strength of the forces between the ions in an ionic compound. Higher lattice energy indicates stronger ionic bonds, making it more difficult for the solid to dissociate into its constituent ions in a solvent, such as water.
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Lattice Energy

Solubility

Solubility refers to the ability of a substance to dissolve in a solvent, forming a homogeneous solution. For ionic compounds, solubility is influenced by the balance between lattice energy and the energy released when ions interact with solvent molecules. If the lattice energy is too high compared to the solvation energy, the compound will be less soluble.
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Hydration Energy

Hydration energy is the energy released when ions are surrounded by water molecules. This process helps to stabilize the ions in solution. For an ionic substance to dissolve, the hydration energy must be sufficient to overcome the lattice energy. If the lattice energy is significantly greater, the compound will not dissolve well in water.
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Related Practice
Textbook Question
Two beakers, one with pure water (blue) and the other with a solution of NaCl in water (green), are placed in a closed container as represented by drawing (a). Which of the draw- ings (b)–(d) represents what the beakers will look like after a substantial amount of time has passed?

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Textbook Question
If a single 5-g block of NaCl is placed in water, it dissolves slowly, but if 5 g of powdered NaCl is placed in water, it dis- solves rapidly. Explain.
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Which would you expect to have the larger hydration energy, SO42- or ClO4-? Explain.
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Classify the strongest type of intermolecular force in the follow- ing interactions: solvent–solvent, solvent–solute, and solute– solute when solid iodine 1I22 is placed in the water. Based on these interactions, predict whether I2 is soluble in water.