Q: A sample of ethanol ($$C_2H_5OH) is $$heated from $$25\ ^\circ C to $$its boiling point. Which of the following equations would you use to calculate the energy required to vaporize 50.0 g of ethanol at its boiling point? (Given: $$\Delta H_{vap}$$ for ethanol = $$38.6\ \mathrm{kJ/mol}$$, molar mass = $$46.07\ \mathrm{g/mol})$$

$$q = n \times \Delta H_{vap}$$, where $$n = \frac{50.0}{46.07}$$

Q: A 100.0 g sample of ice at $$0\ ^\circ C is $$melted. If the heat of fusion ($$\Delta H_{fus}) $$for water is $$6.01\ \mathrm{kJ/mol}$$, how much energy is required? (Molar mass of $$H_2O = 18.02\ \mathrm{g/mol})$$

$$q = n \times \Delta H_{fus} = \frac{100.0}{18.02} \times 6.01 = 33.4\ \mathrm{kJ}$$

Question 1

Which of the following best explains why water has a much higher boiling point than methane, even though both are small molecules?

Accepted Answer

Water molecules form hydrogen bonds, which are stronger than the London dispersion forces present in methane.

Question 2

Which type of crystalline solid is diamond an example of?

Accepted Answer

Covalent network solid

Question 3

A sample of ethanol ($$C_2H_5OH) is $$heated from $$25\ ^\circ C to $$its boiling point. Which of the following equations would you use to calculate the energy required to vaporize 50.0 g of ethanol at its boiling point? (Given: $$\Delta H_{vap}$$ for ethanol = $$38.6\ \mathrm{kJ/mol}$$, molar mass = $$46.07\ \mathrm{g/mol})$$

Accepted Answer

$$q = n 	imes \Delta H_{vap}$$, where $$n = \frac{50.0}{46.07}$$

Question 4

Which of the following substances would you expect to have the lowest melting point?

Accepted Answer

Argon ($$Ar)$$

Question 5

Which statement correctly describes the difference between London dispersion forces and hydrogen bonding?

Accepted Answer

London dispersion forces are present in all molecules, while hydrogen bonding only occurs when hydrogen is bonded to N, O, or F.

Question 6

Which of the following best describes an allotrope?

Accepted Answer

Different structural forms of the same element in the same physical state.

Question 7

A 100.0 g sample of ice at $$0\ ^\circ C is $$melted. If the heat of fusion ($$\Delta H_{fus}) $$for water is $$6.01\ \mathrm{kJ/mol}$$, how much energy is required? (Molar mass of $$H_2O = 18.02\ \mathrm{g/mol})$$

Accepted Answer

$$q = n 	imes \Delta H_{fus} = \frac{100.0}{18.02} 	imes 6.01 = 33.4\ \mathrm{kJ}$$

Question 8

Which of the following is the correct order of increasing strength of intermolecular forces?

Accepted Answer

London dispersion \u003c dipole-dipole \u003c hydrogen bonding

Question 9

Which property is most directly related to the strength of intermolecular forces in a substance?

Accepted Answer

Boiling point

Question 10

Which of the following best explains why iodine ($$I_2) is a $$solid at room temperature while chlorine ($$Cl_2) is a $$gas?

Accepted Answer

Iodine has stronger London dispersion forces due to its larger number of electrons.

Question 11

Which of the following is NOT a type of crystalline solid?

Accepted Answer

Amorphous solid

Question 12

A scientist is comparing the boiling points of $$NH_3$$, $$H_2O$$, and $$HF. $$Which statement best explains the trend observed?

Accepted Answer

$$H_2O$$ has the highest boiling point due to the strongest hydrogen bonding among the three.

Question 13

Which of the following scenarios best illustrates the application of heat of vaporization in a real-world context?

Accepted Answer

Calculating the energy required to boil water in a kettle.

Question 14

Which of the following substances would be expected to have the strongest London dispersion forces?

Accepted Answer

Xenon ($$Xe)$$

Question 15

Which of the following is a correct statement about the melting point of ionic solids compared to molecular solids?

Accepted Answer

Ionic solids generally have higher melting points due to strong electrostatic forces between ions.

Question 16

Which of the following is an example of a dipole-dipole interaction?

Accepted Answer

The attraction between $$HCl$$ molecules.

Question 17

A chemist wants to freeze a sample of benzene ($$C_6H_6) at $$its freezing point. Which property is most relevant to this process?

Accepted Answer

Heat of fusion ($$\Delta H_{fus})$$

Question 18

Which of the following best describes why metallic solids conduct electricity?

Accepted Answer

They have delocalized electrons that move freely throughout the solid.

Question 19

Which of the following is a real-life example of an allotrope?

Accepted Answer

Diamond and graphite, both forms of carbon.

Chapter 12: Liquids, Solids, and Intermolecular Forces - Study Guide

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