An ionic compound has a very negative \(\Delta H_{\text {soln }}\) in water. Would you expect it to be very soluble or nearly insoluble in water? Explain in terms of the enthalpy and entropy changes that accompany the process.

Short Answer

Expert verified
An ionic compound with a very negative \(\Delta H_{\text{soln}}\) in water is likely to be very soluble in water. This is because the dissolution process is exothermic, releasing energy which favors solubility. Also, the dissolution leads to an increase in entropy (disorder), which is typically associated with spontaneous processes. Since both enthalpy and entropy changes favor solubility, we can expect the ionic compound to be highly soluble in water.

Step by step solution

01

Understand the given information

We know that the ionic compound has a very negative ΔHsoln in water, which means that the dissolution process is exothermic (releases heat).
02

Understand the concept of solubility

The solubility of a substance is defined as the maximum amount of it that can dissolve in a certain amount of solvent at a specific temperature. In general, the solubility of a substance increases with increasing temperature, and an increase of entropy (ΔS) usually favors solubility.
03

Analyze the enthalpy change (ΔH)

A negative ΔHsoln indicates that the dissolution process is exothermic. As a result, the attractive forces between the ions in the ionic compound and the water molecules are stronger than the attractive forces holding the ions together in the ionic solid. The dissolution process releases energy, which is favorable for solubility.
04

Analyze the entropy change (ΔS)

When an ionic compound dissolves in water, the ions in the solid separate into free ions in the aqueous solution. This process leads to an increase in the disorder or randomness (i.e., an increase in entropy, ΔS) of the system. Since an increase in entropy is typically associated with spontaneous processes, the dissolution of the ionic compound in water will likely be favored.
05

Combine enthalpy and entropy effects

The dissolution of the ionic compound in water is accompanied by both a negative ΔH (favorable) and an increase in ΔS (favorable). Therefore, we can expect the ionic compound to be very soluble in water.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Two beakers are placed in a sealed box at \(25^{\circ} \mathrm{C}\). One beaker contains \(30.0 \mathrm{~mL}\) of a \(0.050 \mathrm{M}\) aqueous solution of a nonvolatile nonelectrolyte. The other beaker contains \(30.0 \mathrm{~mL}\) of a \(0.035 \mathrm{M}\) aqueous solution of \(\mathrm{NaCl}\). The water vapor from the two solutions reaches equilibrium. (a) In which beaker does the solution level rise, and in which one does it fall? (b) What are the volumes in the two beakers when equilibrium is attained, assuming ideal behavior?

(a) Why does a \(0.10 m\) aqueous solution of NaCl have a higher boiling point than a \(0.10 \mathrm{~m}\) aqueous solution of \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6} ?\) (b) Calculate the boiling point of each solution. (c) The experimental boiling point of the \(\mathrm{NaCl}\) solution is lower than that calculated, assuming that \(\mathrm{NaCl}\) is completely dissociated in solution. Why is this the case?

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) \(\mathrm{KCl}\) in water, (b) \(\mathrm{CH}_{2} \mathrm{Cl}_{2}\) in benzene \(\left(\mathrm{C}_{6} \mathrm{H}_{6}\right),(\mathrm{c})\) methanol \(\left(\mathrm{CH}_{3} \mathrm{OH}\right)\) in water.

Most fish need at least 4 ppm dissolved \(\mathrm{O}_{2}\) for survival. (a) What is this concentration in \(\mathrm{mol} / \mathrm{L} ?\) (b) What partial pressure of \(\mathrm{O}_{2}\) above the water is needed to obtain this concentration at \(10^{\circ} \mathrm{C} ?\) (The Henry's law constant for \(\mathrm{O}_{2}\) at this temperature is \(\left.1.71 \times 10^{-3} \mathrm{~mol} / \mathrm{L}-\mathrm{atm} .\right)\)

(a) What is an ideal solution? (b) The vapor pressure of pure water at \(60^{\circ} \mathrm{C}\) is 149 torr. The vapor pressure of water over a solution at \(60^{\circ} \mathrm{C}\) containing equal numbers of moles of water and ethylene glycol (a nonvolatile solute) is 67 torr. Is the solution ideal according to Raoult's law? Explain.

See all solutions

Recommended explanations on Chemistry Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free