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Chapter 11: Problem 47

Indicate whether each statement is true or false: (a) The critical pressure of a substance is the pressure at which it turns into a solid at room temperature. \((\mathbf{b})\) The critical temperature of a substance is the highest temperature at which the liquid phase can form. (c) Generally speaking, the higher the critical temperature of a substance, the lower its critical pressure. (d) In general, the more intermolecular forces there are in a substance, the higher its critical temperature and pressure.

Short Answer

Expert verified
(a) False: The critical pressure of a substance is for the liquid-gas phase change, not for solid formation. (b) True: The critical temperature represents the highest temperature at which the liquid phase can form. (c) False: Higher critical temperatures do not necessarily imply lower critical pressures. The relationship is complex and depends on other factors. (d) True: Stronger intermolecular forces generally result in higher critical temperatures and pressures, as more energy is required to cause a phase change.

Step by step solution

01

Statement (a) Evaluation

The critical pressure of a substance is the pressure at which it turns into a solid at room temperature. This statement is false. The critical pressure of a substance is the pressure required to cause a phase change between its liquid and gas states at the critical temperature, which is above the solid phase but below the gas phase.
02

Statement (b) Evaluation

The critical temperature of a substance is the highest temperature at which the liquid phase can form. This statement is true. When a substance reaches its critical temperature, it is no longer possible to distinguish between its liquid and gas phases. Above the critical temperature, the substance exists only in the gas phase.
03

Statement (c) Evaluation

Generally speaking, the higher the critical temperature of a substance, the lower its critical pressure. This statement is false. There is no direct rule that suggests that a substance with a higher critical temperature will have a lower critical pressure. Instead, the relationship is complex and depends on other factors like molecular structure and intermolecular forces.
04

Statement (d) Evaluation

In general, the more intermolecular forces there are in a substance, the higher its critical temperature and pressure. This statement is true. Intermolecular forces are the attractive forces between molecules. The stronger these forces, the more resistant the substance is to undergoing phase changes. As a result, substances with stronger intermolecular forces typically have higher critical temperatures and pressures because they require more energy to cause a phase change.

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Most popular questions from this chapter

(a) Do you expect the viscosity of glycerol, $\mathrm{C}_{3} \mathrm{H}_{5}(\mathrm{OH})_{3}$, to be larger or smaller than that of 1 -propanol, \(\mathrm{C}_{3} \mathrm{H}_{7} \mathrm{OH} ?\) (b) Explain. [Section 11.3\(]\)

At room temperature, \(\mathrm{CO}_{2}\) is a gas, \(\mathrm{CCl}_{4}\) is a liquid, and \(\mathrm{C}_{60}\) (fullerene) is a solid. List these substances in order of (a) increasing intermolecular energy of attraction and (b) increasing boiling point.

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