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Ch.13 - Properties of Solutions
All textbooksBrown 15th EditionCh.13 - Properties of SolutionsProblem 13
Chapter 13, Problem 13

Indicate whether each statement is true or false: (a) A solute will dissolve in a solvent if solute–solute interactions are weaker than solute–solvent interactions. (b) In making a solution, the enthalpy of mixing is always a positive number. (c) An increase in entropy favors mixing.

Verified step by step guidance
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Step 1: Consider statement (a). Recall that a solute will dissolve in a solvent if the interactions between the solute and solvent are stronger than the interactions between solute particles themselves. This is because the energy released from solute-solvent interactions can compensate for the energy required to separate solute particles.
Step 2: Evaluate statement (b). Understand that the enthalpy of mixing, \( \Delta H_{mix} \), can be either positive or negative. It depends on the balance between the energy required to break solute-solute and solvent-solvent interactions and the energy released from forming solute-solvent interactions.
Step 3: Analyze statement (c). Remember that entropy, a measure of disorder, generally increases when substances mix. This increase in entropy is a driving force for mixing, as systems tend to move towards greater disorder.
Step 4: For statement (a), determine if the condition described (solute-solute interactions being weaker than solute-solvent interactions) would lead to dissolution based on the principles of energetics and interactions.
Step 5: For statement (b), consider examples of exothermic and endothermic mixing processes to understand that the enthalpy change can vary, and for statement (c), relate the concept of entropy to the natural tendency of systems to mix.

Key Concepts

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

Solute-Solvent Interactions

The ability of a solute to dissolve in a solvent is largely determined by the interactions between solute and solvent molecules. If the interactions between solute-solute are weaker than those between solute-solvent, the solute is likely to dissolve. This principle is often summarized by the phrase 'like dissolves like,' indicating that polar solutes dissolve well in polar solvents, while nonpolar solutes dissolve in nonpolar solvents.
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Solution Components

Enthalpy of Mixing

The enthalpy of mixing refers to the heat change that occurs when solute and solvent are combined to form a solution. This value can be positive or negative, depending on the nature of the interactions involved. A positive enthalpy of mixing indicates that energy is absorbed during the process, while a negative value suggests that energy is released. It is not accurate to state that this value is always positive, as it varies with different solute-solvent combinations.
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Entropy and Mixing

Entropy is a measure of disorder or randomness in a system, and an increase in entropy generally favors the mixing of substances. When a solute dissolves in a solvent, the overall disorder of the system increases, which is thermodynamically favorable. This concept is crucial in understanding why certain solutes dissolve in solvents, as the drive towards greater entropy can often overcome unfavorable enthalpic contributions.
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Related Practice
Textbook Question

This portion of a phase diagram shows the vapor–pressure curves of a volatile solvent and of a solution of that solvent containing a nonvolatile solute. (b) What are the normal boiling points of the solvent and the solution? [Section 13.5]

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Textbook Question

Suppose you had a balloon made of some highly flexible semipermeable membrane. The balloon is filled completely with a 0.2 M solution of some solute and is submerged in a 0.1 M solution of the same solute:

Initially, the volume of solution in the balloon is 0.25 L. Assuming the volume outside the semipermeable membrane is large, as the illustration shows, what would you expect for the solution volume inside the balloon once the system has come to equilibrium through osmosis? [Section 13.5]

Textbook Question

The diagrams shown represent an emulsion, a true solution, and a liquid crystal. The colored balls represent different liquid molecules. Which diagram corresponds to which type of mixture? [Section 13.6]

Textbook Question

Indicate the type of solute–solvent interaction that should be most important in each of the following solutions: a. CCl4 in benzene (C6H6),

Textbook Question

Indicate the type of solute–solvent interaction that should be most important in each of the following solutions: b. methanol (CH3OH) in water,