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Chapter 9: Problem 71

Criticize or comment on each of the following statements. (a) Vapor pressure remains constant regardless of volume. (b) The only forces that affect boiling point are dispersion forces. (c) The strength of the covalent bonds within a molecule has no effect on the melting point of the molecular substance. (d) A compound at its critical temperature is always a gas regardless of pressure.

Short Answer

Expert verified
Answer: Vapor pressure remains constant regardless of volume.

Step by step solution

01

(a) Vapor pressure remains constant regardless of volume.

This statement is accurate. Vapor pressure is the pressure exerted by the vapor in equilibrium with its condensed phase (liquid or solid) at a given temperature. It is an intrinsic property of a substance and does not depend on the volume of the container. The vapor pressure depends solely on the temperature and the nature of the substance, but not on the volume.
02

(b) The only forces that affect boiling point are dispersion forces.

This statement is not accurate. Boiling point is affected by various intermolecular forces, including dispersion or London forces, hydrogen bonding, and dipole-dipole interactions. Stronger intermolecular forces result in a higher boiling point as more energy is required to break these forces and convert a liquid into a gas. While dispersion forces are present in all molecules, they are not the only forces that impact boiling point.
03

(c) The strength of the covalent bonds within a molecule has no effect on the melting point of the molecular substance.

This statement is generally accurate. The melting point of a molecular substance is mainly determined by the strength of intermolecular forces, not the strength of covalent bonds within a molecule. Strong covalent bonds indicate stable molecules with high bond dissociation energies, but they do not necessarily correlate with the strength of intermolecular forces that hold the molecules together in the solid phase. However, some covalent substances, like diamond and graphite, have covalent bonds that extend throughout the entire crystal lattice, and in such cases, the melting point can be more influenced by the strength of the covalent bonds.
04

(d) A compound at its critical temperature is always a gas regardless of pressure.

This statement is not accurate. At the critical temperature, a substance can exist in both liquid and gas phases, depending on the pressure applied. Above the critical temperature and pressure, a substance enters a unique state called the supercritical fluid phase, in which it exhibits properties of both liquids and gases. Thus, a compound at its critical temperature is not always in a gaseous state but can also exist as a supercritical fluid when above the critical pressure.

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Most popular questions from this chapter

The data below give the vapor pressure of octane, a major component of gasoline. \(\begin{array}{lllcl}\text { vp }(\mathrm{mm} \mathrm{Hg}) & 10 & 40 & 100 & 400 \\ t\left({ }^{\circ} \mathrm{C}\right) & 19.2 & 45.1 & 65.7 & 104.0\end{array}\) Plot ln vp versus \(1 / T\). Use your graph to estimate the heat of vaporization of octane. \(\left(\ln P=A-\frac{\Delta H_{\mathrm{vap}}}{R}\left(\frac{1}{T}\right)\right.\), where \(A\) is the \(y\) -intercept and \(\Delta H_{\mathrm{vap}}\) is the slope.)

Describe the structural units in (a) NaI (b) \(\mathrm{N}_{2}\) (c) \(\mathrm{KO}_{2}\) (d) \(\mathrm{Au}\)

Of the four general types of solids, which one(s) (a) are generally low-boiling? (b) are ductile and malleable? (c) are generally soluble in nonpolar solvents?

In which of the following processes is it necessary to break covalent bonds as opposed to simply overcoming intermolecular forces? (a) melting mothballs made of naphthalene (b) dissolving HBr gas in water to form hydrobromic acid (c) vaporizing ethyl alcohol, \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}\) (d) changing ozone, \(\mathrm{O}_{3}\), to oxygen gas, \(\mathrm{O}_{2}\)

What are the strongest attractive forces that must be overcome to (a) boil silicon hydride \(\mathrm{SiH}_{4} ?\) (b) vaporize calcium chloride? (c) dissolve \(\mathrm{Cl}_{2}\) in carbon tetrachloride, \(\mathrm{CCl}_{4} ?\) (d) melt iodine?
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