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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 stronger 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.

Short Answer

Expert verified
Statement (a) is false because a solute will dissolve in a solvent if solute-solvent interactions are stronger than solute-solute interactions. Statement (b) is false because the enthalpy of mixing can be either positive or negative, not always positive. Statement (c) is true since an increase in entropy, which represents an increase in disorder, favors mixing.

Step by step solution

01

Statement (a) analysis

To determine if statement (a) is true or false, we need to understand when a solute will dissolve in a solvent. A solute will dissolve in a solvent if solute-solvent interactions are stronger than solute-solute interactions. In this case, the statement says a solute will dissolve if solute-solute interactions are stronger, which is not correct. Therefore, statement (a) is false.
02

Statement (b) analysis

To determine if statement (b) is true or false, we need to understand the concept of enthalpy of mixing. The enthalpy of mixing refers to the energy change when two substances mix together, which can be either positive (endothermic) or negative (exothermic). The statement claims that the enthalpy of mixing is always a positive number, which is not true. It can be either positive or negative depending on the substances involved. Hence, statement (b) is false.
03

Statement (c) analysis

To determine if statement (c) is true or false, we need to understand the concept of entropy. Entropy is a measure of the randomness or disorder of a system. An increase in entropy means that the system becomes more disordered or random, which is generally favored in reactions. In the context of mixing, an increase in entropy implies that the molecules become more dispersed, which favors mixing. So, statement (c) is true.

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Most popular questions from this chapter

\(\mathrm{KBr}\) is relatively soluble in water, yet its enthalpy of solution is \(+19.8 \mathrm{~kJ} / \mathrm{mol}\). Which of the following statements provides the best explanation for this behavior? (a) Potassium salts are always soluble in water. (b) The entropy of mixing must be unfavorable. (c) The enthalpy of mixing must be small compared to the enthalpies for breaking up water-water interactions and K-Br ionic interactions. (d) \(\mathrm{KBr}\) has a high molar mass compared to other salts like \(\mathrm{NaCl}\)

Aerosols are important components of the atmosphere. Does the presence of aerosols in the atmosphere increase or decrease the amount of sunlight that arrives at the Earth's surface, compared to an "aerosol-free" atmosphere? Explain your reasoning.

You make two solutions of a nonvolatile solute with a liquid solvent, $0.01 \mathrm{M}\( and \)1.00 \mathrm{M}$. Indicate whether each of the following statements is true or false. (a) The vapor pressure of the concentrated solution is higher than that of the diluted solution. (b) The osmotic pressure of the concentrated solution is higher than that of the diluted solution. (c) The boiling point of the concentrated solution is higher than that of the diluted solution. (d) The freezing point of the concentrated solution is higher than that of the diluted solution.

Common laboratory solvents include acetone $\left(\mathrm{CH}_{3} \mathrm{COCH}_{3}\right)\(, methanol \)\left(\mathrm{CH}_{3} \mathrm{OH}\right)\(, toluene \)\left(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CH}_{3}\right),$ and water. Which of these is the best solvent for nonpolar solutes?

At \(35^{\circ} \mathrm{C}\) the vapor pressure of acetone, \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CO},\) is 47.9 \(\mathrm{kPa}\), and that of carbon disulfide, \(\mathrm{CS}_{2}\), is \(66.7 \mathrm{kPa}\). A solution composed of an equal number of moles of acetone and carbon disulfide has a vapor pressure of \(86.7 \mathrm{kPa}\) at $35^{\circ} \mathrm{C} .(\mathbf{a})$ What would be the vapor pressure of the solution if it exhibited ideal behavior? (b) Based on the behavior of the solution, predict whether the mixing of acetone and carbon disulfide is an exothermic \(\left(\Delta H_{\text {soln }}<0\right)\) or endothermic $\left(\Delta H_{\text {soln }}>0\right)$ process.
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