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Problem 2
(a) Which kind of intermolecular attractive force is shown in each case here? (b) Predict which of the four interactions is the weakest. [Section 11.2]
- Carbon tetrachloride, CCl4, and chloroform, CHCl3, are common organic liquids. Carbon tetrachloride’s normal boiling point is 77 °C; chloroform’s normal boiling point is 61 °C. Which statement is the best explanation of these data? (a) Chloroform can hydrogen-bond, but carbon tetrachloride cannot. (b) Carbon tetrachloride has a larger dipole moment than chloroform. (c) Carbon tetrachloride is more polarizable than chloroform.
Problem 3
- If 42.0 kJ of heat is added to a 32.0-g sample of liquid meth-ane under 1 atm of pressure at a temperature of -170°C, what are the final state and temperature of the methane once the system equilibrates? Assume no heat is lost to the surroundings. The normal boiling point of methane is -161.5 °C. The specific heats of liquid and gaseous methane are 3.48 and 2.22 J/g-K, respectively. [Section 11.3]
Problem 4
Problem 5a
Using this graph of CS2 data, determine (a) the approximate vapor pressure of CS2 at 30°C,
Problem 6b
The molecules
have the same molecular formula (C3H8O) but different chemical structures. (b) Which molecule do you expect to have a larger dipole moment? [Sections 11.2 and 11.5]
Problem 7b
The phase diagram of a hypothetical substance is
(b) What is the physical state of the substance under the following conditions? (i) T = 150 K, P = 0.2 atm; (ii) T = 100 K, P = 0.8 atm; (iii) T = 300K, P = 1.0atm. [Section 11.6]
- Ethylene glycol (HOCH2CH2OH) and pentane (C5H12) are both liquids at room temperature and room pressure, and have about the same molecular weight. (b) One of these liquids has a much lower normal boiling point (36.1 °C) compared to the other one (198 °C). Which liquid has the lower normal boiling point? (c) One of these liquids is the major component in antifreeze in automobile engines. Which liquid would you expect to be used as antifreeze? (d) One of these liquids is used as a 'blowing agent' in the manufacture of polystyrene foam because it is so volatile. Which liquid would you expect to be used as a blowing agent?
Problem 8
Problem 8a
At three different temperatures, T1, T2, and T3, the molecules in a liquid crystal align in these ways:
(a) At which temperature or temperatures is the substance in a liquid crystalline state? At those temperatures, which type of liquid crystalline phase is depicted?
Problem 8b
At three different temperatures, T1, T2, and T3, the molecules in a liquid crystal align in these ways:
(b) Which is the highest of these three temperatures? [Section 11.7]
- In Table 11.3, we saw that the viscosity of a series of hydrocarbons increased with molecular weight, doubling from the six-carbon molecule to the ten-carbon molecule. (c) The surface tension of the hydrocarbon liquids in Table 11.4 does increase from hexane to decane, but only by a rather small amount (20% overall, compared to the doubling of viscosity). Which of the statements below is the most likely explanation for this phenomenon? (i) The flexibility of the molecules has a much larger effect on viscosity than on surface tension. (ii) Viscosity only depends on molecular weight, but surface tension depends on molecular weight and on intermolecular forces. (iii) Larger molecules can make larger liquid droplets and therefore have lower surface tension.
Problem 9
Problem 9a
List the three states of matter in order of (a) increasing molecular disorder
Problem 9b
List the three states of matter in order of (b) increasing intermolecular attraction.
Problem 10a
(a) How does the average kinetic energy of molecules com- pare with the average energy of attraction between mole- cules in solids, liquids, and gases?
Problem 10c
(c) What happens to a gas if you put it under extremely high pressure?
- As a metal such as lead melts, what happens to (a) the average kinetic energy of the atoms? (b) the average distance between the atoms?
Problem 11
- At room temperature, Si is a solid, CCl4 is a liquid, and Ar is a gas. List these substances in order of (b) increasing boiling point.
Problem 12
Problem 12a
At room temperature, Si is a solid, CCl4 is a liquid, and Ar is a gas. List these substances in order of (a) increasing intermolecular energy of attraction
- At standard temperature and pressure, the molar volumes of Cl2 and NH3 gases are 22.06 and 22.40 L, respectively. (a) Given the different molecular weights, dipole moments, and molecular shapes, why are their molar volumes nearly the same?
Problem 13
Problem 13b
At standard temperature and pressure, the molar volumes of Cl2 and NH3 gases are 22.06 and 22.40 L, respectively (b) On cooling to 160 K, both substances form crystalline solids. Do you expect the molar volumes to decrease or increase on cooling the gases to 160 K?
Problem 13c
At standard temperature and pressure, the molar volumes of Cl2 and NH3 gases are 22.06 and 22.40 L, respectively. (c) The densities of crystalline Cl2 and NH3 at 160 K are 2.02 and 0.84 g/cm3, respectively. Calculate their molar volumes.
Problem 13d
At standard temperature and pressure, the molar volumes of Cl2 and NH3 gases are 22.06 and 22.40 L, respectively (d) Are the molar volumes in the solid state as similar as they are in the gaseous state? Explain.
- Benzoic acid, C6H5COOH, melts at 122 °C. The density in the liquid state at 130 °C is 1.08 g/cm3. The density of solid benzoic acid at 15 °C is 1.266 g/cm3. (a) In which of these two states is the average distance between molecules greater?
Problem 14
Problem 14b
Benzoic acid, C6H5COOH, melts at 122 °C. The density in the liquid state at 130 °C is 1.08 g/cm3. The density of solid benzoic acid at 15 °C is 1.266 g/cm3. (b) If you converted a cubic centimeter of liquid benzoic acid into a solid, would the solid take up more, or less, volume than the original cubic centimeter of liquid?
Problem 15a
(a) Which type of intermolecular attractive force operates between all molecules?
Problem 15b
(b) Which type of intermolecular attractive force operates only between polar molecules?
Problem 15c
(c) Which type of intermolecular attractive force operates only between the hydrogen atom of a polar bond and a nearby small electronegative atom?
- Which is generally stronger, intermolecular interactions or intramolecular interactions?
Problem 16
Problem 16b
(b) Which of these kinds of interactions are broken when a liquid is converted to a gas?
Problem 17
Describe the intermolecular forces that must be overcome to convert these substances from a liquid to a gas: (a) SO2, (b) CH3COOH, (c) H2S.
Problem 18a,d
Which type of intermolecular force accounts for each of these differences? (a) CH3OH boils at 65 °C; CH3SH boils at 6 °C. (d) Acetone boils at 56 °C, whereas 2-methylpropane boils at -12 °C.