As the intermolecular attractive forces between molecules increase in magnitude, do you expect each of the following to increase or decrease in magnitude? (a) Vapor pressure, (b) heat of vaporization, \((\mathbf{c})\) boiling point, \((\mathbf{d})\) freezing point, (e) viscosity, (f) surface tension, \((\mathbf{g})\) critical temperature.

Short Answer

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As intermolecular attractive forces increase: (a) vapor pressure decreases, (b) heat of vaporization increases, (c) boiling point increases, (d) freezing point increases, (e) viscosity increases, (f) surface tension increases, and (g) critical temperature increases. This is due to stronger attractions between molecules, making phase transitions and molecular movements more difficult.

Step by step solution

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(a) Vapor pressure

Vapor pressure is the pressure exerted by a vapor in equilibrium with its condensed phase. When intermolecular forces increase, molecules are more attracted to each other and have a harder time escaping into the vapor phase. As a result, fewer molecules escape, leading to a decrease in vapor pressure.
02

(b) Heat of vaporization

Heat of vaporization is the amount of heat required to transform a given amount of a substance from the liquid phase to the vapor phase. If intermolecular forces increase, more energy is needed to overcome these stronger forces and facilitate the phase transition. Therefore, heat of vaporization will increase.
03

(c) Boiling point

Boiling point is the temperature at which a liquid changes into a vapor when heated. When intermolecular forces increase, molecules need more energy to separate and transition into the vapor phase. As a result, boiling points increase with an increase in intermolecular attractive forces.
04

(d) Freezing point

Freezing point is the temperature at which a liquid changes into a solid when cooled. When intermolecular forces increase, molecules in a substance will experience a stronger attraction to each other. This makes it easier for the system to organize into a more structured solid state, so the freezing point will increase.
05

(e) Viscosity

Viscosity is a measure of a fluid's resistance to flow. When intermolecular forces increase, the attraction between molecules makes it harder for them to move past one another. Hence, higher intermolecular forces lead to an increase in viscosity.
06

(f) Surface tension

Surface tension is the force needed to stretch or break the surface of a liquid. When intermolecular forces increase, there's a stronger attraction between the molecules at the surface, making it more difficult to break those bonds. Consequently, surface tension will increase as intermolecular forces increase.
07

(g) Critical temperature

Critical temperature is the temperature above which a gas cannot be liquefied, regardless of the applied pressure. When intermolecular forces increase, molecules are more attracted to each other, making it easier for them to form a liquid phase. This means that critical temperature will increase as intermolecular attractive forces increase.

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As a metal such as lead melts, what happens to (a) the average kinetic energy of the atoms and (b) the average distance between the atoms?

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