Textbook Question
Indicate the principal type of solute–solvent interaction in each of the following solutions and rank the solutions from weakest to strongest solute–solvent interaction: (a) KCl in water
Ch.13 - Properties of Solutions
Chapter 13, Problem 17
An ionic compound has a very negative ∆Hsoln in water. (a) Would you expect it to be very soluble or nearly insoluble in water?
Verified step by step guidance1
Understand the concept of ∆Hsoln: ∆Hsoln, or the enthalpy of solution, is the change in enthalpy when a solute dissolves in a solvent. A very negative ∆Hsoln indicates that the dissolution process releases a significant amount of energy, making it exothermic.
Consider the solubility principle: Generally, if the dissolution process is exothermic (negative ∆Hsoln), it suggests that the solute is likely to be soluble in the solvent. This is because the release of energy can help overcome the lattice energy of the ionic compound, facilitating its dissolution.
Analyze the energy interactions: When an ionic compound dissolves in water, the energy released from the formation of ion-dipole interactions between the ions and water molecules can be greater than the energy required to break the ionic bonds in the solid lattice.
Relate ∆Hsoln to solubility: A very negative ∆Hsoln implies that the energy released during the formation of these interactions is substantial, which typically enhances the solubility of the compound in water.
Conclude based on the analysis: Given the very negative ∆Hsoln, it is reasonable to expect the ionic compound to be very soluble in water, as the exothermic nature of the dissolution process favors solubility.
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Enthalpy of Solution (∆Hsoln)
The enthalpy of solution (∆Hsoln) refers to the heat change that occurs when a solute dissolves in a solvent. A very negative ∆Hsoln indicates that the dissolution process is exothermic, meaning it releases heat. This release of energy often favors the solubility of the solute in the solvent, as it can lead to a more stable solution.
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Enthalpy of Formation
Ionic Compounds and Solubility
Ionic compounds consist of positively and negatively charged ions held together by strong electrostatic forces. Their solubility in water depends on the balance between the lattice energy of the solid and the energy released when the ions interact with water molecules. A very negative ∆Hsoln suggests that the energy released during solvation is greater than the energy required to break the ionic bonds, leading to higher solubility.
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Factors Affecting Solubility
Solubility is influenced by several factors, including temperature, pressure, and the nature of the solute and solvent. For ionic compounds, the polarity of the solvent and the strength of the ionic bonds play crucial roles. In the case of a very negative ∆Hsoln, it indicates that the compound is likely to be very soluble in water, as the dissolution process is energetically favorable.
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Related Practice
Textbook Question
Indicate the principal type of solute–solvent interaction in each of the following solutions and rank the solutions from weakest to strongest solute–solvent interaction: (b) CH2Cl2 in benzene (C6H6)
Textbook Question
Indicate the principal type of solute–solvent interaction in each of the following solutions and rank the solutions from weakest to strongest solute–solvent interaction: (c) methanol (CH3OH) in water
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Textbook Question
An ionic compound has a very negative ∆Hsoln in water (b) Which term would you expect to be the largest negative number: ∆Hsolvent, ∆Hsolute, or ∆Hmix?
Textbook Question
When ammonium chloride dissolves in water, the solution becomes colder. (a) Is the solution process exothermic or endothermic?
Textbook Question
When ammonium chloride dissolves in water, the solution becomes colder. (b) Why does the solution form?