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Chapter 11: Problem 52

True or false: \((\mathbf{a}) \mathrm{CBr}_{4}\) is more volatile than \(\mathrm{CCl}_{4}\). (b) \(\mathrm{CBr}_{4}\) has a higher boiling point than \(\mathrm{CCl}_{4}\). (c) \(\mathrm{CBr}_{4}\) has weaker intermolecular forces than \(\mathrm{CCl}_{4}\). (d) \(\mathrm{CBr}_{4}\) has a higher vapor pressure at the same temperature than \(\mathrm{CCl}_{4}\).

Short Answer

Expert verified
(a) False, (b) True, (c) False, and (d) False.

Step by step solution

01

Analyzing Intermolecular Forces

Both \(\mathrm{CCl}_{4}\) and \(\mathrm{CBr}_{4}\) are nonpolar molecules due to their tetrahedral structure and balanced distribution of electronegativity. Therefore, their main intermolecular forces are London dispersion forces. London dispersion forces depend on polarizability: the ease with which the electron cloud of an atom or molecule can be distorted. Generally, larger atoms or molecules have a more easily distorted electron cloud, leading to stronger London dispersion forces. Bromine atoms are larger and more polarizable than chlorine atoms, resulting in stronger London dispersion forces for \(\mathrm{CBr}_{4}\) compared to \(\mathrm{CCl}_{4}\). Now, let's evaluate each statement:
02

Statement (a): Volatility

Volatility refers to the tendency of a substance to vaporize. A substance with stronger intermolecular forces will require more energy to break those forces and vaporize, making it less volatile. Since \(\mathrm{CBr}_{4}\) has stronger London dispersion forces than \(\mathrm{CCl}_{4}\), it is less volatile. This statement is False.
03

Statement (b): Boiling Point

The boiling point is the temperature at which the vapor pressure of a liquid becomes equal to the atmospheric pressure. A higher boiling point corresponds to stronger intermolecular forces. As we have discussed, \(\mathrm{CBr}_{4}\) has stronger London dispersion forces than \(\mathrm{CCl}_{4}\). Thus, it has a higher boiling point, making this statement True.
04

Statement (c): Intermolecular Forces

We have already established that \(\mathrm{CBr}_{4}\) has stronger London dispersion forces than \(\mathrm{CCl}_{4}\). This statement claims that \(\mathrm{CBr}_{4}\) has weaker intermolecular forces, which contradicts our analysis. Therefore, this statement is False.
05

Statement (d): Vapor Pressure at the Same Temperature

At a given temperature, a substance with weaker intermolecular forces will have a higher vapor pressure. Since \(\mathrm{CBr}_{4}\) has stronger intermolecular forces than \(\mathrm{CCl}_{4}\), its vapor pressure at the same temperature will be lower. This statement is False. In summary, the solutions to each statement are: (a) False, (b) True, (c) False, and (d) False.

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Most popular questions from this chapter

(a) Place the following substances in order of increasing volatility: $\mathrm{CH}_{4}, \mathrm{CBr}_{4}, \mathrm{CH}_{2} \mathrm{Cl}_{2}, \mathrm{CH}_{3} \mathrm{Cl}, \mathrm{CHBr}_{3},\( and \)\mathrm{CH}_{2} \mathrm{Br}_{2}$. (b) How do the boiling points vary through this series? (c) Explain your answer to part (b) in terms of intermolecular forces.

Which member in each pair has the greater dispersion forces? (a) \(\mathrm{CH}_{3} \mathrm{OH}\) or $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH},\( (b) \)\mathrm{NH}_{3}$ or \(\mathrm{N}\left(\mathrm{CH}_{3}\right)_{3}\), (c) $\mathrm{CH}_{2} \mathrm{Cl}_{2}\( or \)\mathrm{CH}_{2} \mathrm{Br}_{2}$

Ethylene glycol \(\left(\mathrm{HOCH}_{2} \mathrm{CH}_{2} \mathrm{OH}\right)\) and pentane \(\left(\mathrm{C}_{5} \mathrm{H}_{12}\right)\) are both liquids at room temperature and room pressure, and have about the same molecular weight. (a) One of these liquids is much more viscous than the other. Which one do you predict is more viscous? (b) One of these liquids has a much lower normal boiling point \(\left(36.1^{\circ} \mathrm{C}\right)\) compared to the other one \(\left(198^{\circ} \mathrm{C}\right)\). Which liquid has the lower normal boiling point? (c) One of these liquids is the major component in antifreeze in automobile engines. Which liquid would you expect to be used as antifreeze? (d) One of these liquids is used as a "blowing agent" in the manufacture of polystyrene foam because it is so volatile. Which liquid would you expect to be used as a blowing agent?

(a) How does the average kinetic energy of molecules compare with the average energy of attraction between molecules in solids, liquids, and gases? (b) Why does increasing the temperature cause a solid substance to change in succession from a solid to a liquid to a gas? (c) What happens to a gas if you put it under extremely high pressure?

The vapor pressure of acetone \(\left(\mathrm{CH}_{3} \mathrm{COCH}_{3}\right)\) at \(19^{\circ} \mathrm{C}\) is 5.33 kPa. A 3.50-g sample of acetone is placed in a \(2.00 \mathrm{~L}\) container at \(22^{\circ} \mathrm{C}\). If the container is closed and the acetone is allowed to reach equilibrium with its vapor, how many grams of liquid acetone remain? (Assume that the vapor behaves like an ideal gas.)
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