Question 1

Which of the following molecules can form hydrogen bonds with other molecules of the same kind?

Accepted Answer

H2NNH2

Question 2

Why does ice float on liquid water?

Accepted Answer

Hydrogen bonding in ice forces water molecules farther apart, making ice less dense than liquid water.

Question 3

Which of the following best explains why NaCl dissolves in water?

Accepted Answer

Ion–dipole interactions between Na+ and Cl– ions and water molecules overcome the lattice energy of NaCl.

Question 4

Which of the following substances would you expect to have the highest boiling point?

Accepted Answer

BaCl2

Question 5

Which of the following statements about viscosity is correct?

Accepted Answer

Viscosity increases with stronger intermolecular forces and decreases with higher temperature.

Question 6

What is the main reason water beads up on a freshly waxed car surface?

Accepted Answer

Surface tension due to strong hydrogen bonding between water molecules.

Question 7

Which process is endothermic?

Accepted Answer

Vaporization

Question 8

Calculate the amount of heat required to convert 2.00 mol of ice at 0 °C to liquid water at 0 °C. The heat of fusion of ice is $$\Delta H_{fus} = 6.01\ \mathrm{kJ/mol}.$$

Accepted Answer

$$12.02\ \mathrm{kJ}$$

Question 9

Which of the following best describes a supercritical fluid?

Accepted Answer

A state where the liquid and gas phases are indistinguishable.

Question 10

A liquid boils when its vapor pressure equals the external pressure. If the external pressure is reduced, what happens to the boiling point?

Accepted Answer

It decreases.

Question 11

Which of the following molecules exhibits only dispersion forces as its strongest intermolecular force?

Accepted Answer

Ne

Question 12

Why does water have a much higher critical temperature than methane?

Accepted Answer

Water molecules form strong hydrogen bonds.

Question 13

Which of the following best explains why DNA strands are held together in a double helix?

Accepted Answer

Hydrogen bonds between complementary bases.

Question 14

Which of the following is true about capillary action in a glass tube containing water?

Accepted Answer

Adhesive forces between water and glass are stronger than cohesive forces between water molecules.

Question 15

Which of the following phase changes is exothermic?

Accepted Answer

Condensation

Question 16

A sample of octane has a viscosity of $$5.42 	imes 10$$^{-4}$$\ \mathrm{kg/(m\cdot s)} at$$ $$20\ ^\circ\mathrm{C}. $$What will happen to its viscosity if the temperature is increased to $$40\ ^\circ\mathrm{C}$$?

Accepted Answer

Viscosity will decrease.

Question 17

Which of the following best describes the relationship between intermolecular forces and vapor pressure?

Accepted Answer

Weaker intermolecular forces result in higher vapor pressure.

Question 18

Which of the following is the strongest type of intermolecular force present in liquid ammonia (NH3)?

Accepted Answer

Hydrogen bonding

Question 19

A heating curve for water shows a flat region at 100 °C. What is happening in this region?

Accepted Answer

Liquid water is being converted to steam at constant temperature.

Question 20

Which of the following best explains why longer hydrocarbon chains have higher viscosity?

Accepted Answer

They have stronger intermolecular forces and are more likely to become entangled.

Intermolecular Forces and Their Effects on Physical Properties

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