3.1-3.3 Intermolecular Forces & Properties

Multiple Choice

The diagram above is a molecular model of a gaseous diatomic element that is just above its boiling point. Intermolecular forces between the gas molecules will cause them to condense into the liquid phase if the temperature is lowered. Which of the following best describes how the model is limited in its depiction of the phenomenon?

• It does not show how hydrogen bonds are constantly forming, breaking, and reforming, which results in a net force of attraction between the molecules.

• It does not show how the interactions between ions and the induced molecular dipoles result in a net force of attraction between the molecules

• It does not show how the interacting permanent dipoles of the molecules result in a net force of attraction between the molecules.

• It does not show how the temporary fluctuating dipoles of the molecular electron clouds result in a net force of attraction between the molecules

Multiple Choice

The electron cloud of HF is smaller than that of F2 , however, HF has a much higher boiling point than F2 has. Which of the following explains how the dispersion-force model of intermolecular attraction does not account for the unusually high boiling point of HF?

• F2 is soluble in water, whereas HF is insoluble in water

• The F2 molecule has a greater mass than the HF molecule has 

• Liquid F2 has weak dispersion force attractions between its molecules, whereas liquid HF has strong ionic interactions between H+ and F− ions

• Liquid F2 has weak dispersion force attractions between its molecules, whereas liquid HF has both weak dispersion force attractions and hydrogen bonding interactions between its molecules.

Multiple Choice

Four different liquid compounds in flasks at 20°C are represented above. The table below identifies the compounds. Flask C shows the most particles in the vapor phase. Which of the following is not shown in the model but best helps to explain why flask C must contain pentane?

• The random motion of the particles within the liquie

• The relative speeds of the vapor particles in each flask

• The strength of the intermolecular forces between the particles in the liquids

• The structural formula of the molecules of the liquid and vapor in each flask

Multiple Choice

Of the following, the best explanation for the fact that most gases are easily compressed is that the molecules in a gas

• are in constant motion

• are relatively far apart

• have relatively small masses

• have a real, nonzero volume

• move slower as temperature decreases

Open Ended

Which compound has the higher boiling point? Justify your answer. The type(s) of intermolecular force(s) in both substances should be included in your answer.

Open Ended

Type 2 questions you still have. 

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