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- (b) Could you measure the triple point of water by measuring the temperature in a vessel in which water vapor, liquid water, and ice are in equilibrium under 1 atm of air? Explain.
Problem 58
Problem 60a
Referring to Figure 11.29, describe the phase changes (and the temperatures at which they occur) when CO2 is heated from -80 to -20°C at (a) a constant pressure of 3 atm,
Problem 61a
The phase diagram for neon is
Use the phase diagram to answer the following questions. (a) What is the approximate value of the normal melting point?
Problem 62a
Use the phase diagram of neon to answer the following questions. (a) What is the approximate value of the normal boiling point?
Problem 62b
Use the phase diagram of neon to answer the following questions. (b) What can you say about the strength of the intermolecular forces in neon and argon based on the critical points of Ne and Ar (see Table 11.5.)?
Problem 64
At 25 °C gallium is a solid with a density of 5.91 g/cm3. Its melting point, 29.8 °C, is low enough that you can melt it by holding it in your hand. The density of liquid gallium just above the melting point is 6.1 g/cm3. Based on this information, what unusual feature would you expect to find in the phase diagram of gallium?
- In terms of the arrangement and freedom of motion of the molecules, how are the nematic liquid crystalline phase and an ordinary liquid phase similar? How are they different?
Problem 65
- What observations made by Reinitzer on cholesteryl benzoate suggested that this substance possesses a liquid crystalline phase?
Problem 66
Problem 67a,b,d,e,f
Indicate whether each statement is true or false: (a) The liquid crystal state is another phase of matter, just like solid, liquid, and gas. (b) Liquid crystalline molecules are generally spherical in shape. (d) Molecules that exhibit a liquid crystalline phase show weaker-than-expected intermolecular forces. (e) Molecules containing only carbon and hydrogen are likely to form liquid crystalline phases. (f) Molecules can exhibit more than one liquid crystalline phase.
Problem 67c
Indicate whether each statement is true or false: (c) Molecules that exhibit a liquid crystalline phase do so at well-defined temperatures and pressures.
Problem 69
For a given substance, the liquid crystalline phase tends to be more viscous than the liquid phase. Why?
- It often happens that a substance possessing a smectic liquid crystalline phase just above the melting point passes into a nematic liquid crystalline phase at a higher temperature. Account for this type of behavior.
Problem 71
- As the intermolecular attractive forces between molecules increase in magnitude, do you expect the heat of vaporization to increase or decrease in magnitude?
Problem 73
Problem 73b
As the intermolecular attractive forces between molecules increase in magnitude, do you expect each of the following to increase or decrease in magnitude? (b) heat of vaporization,
Problem 73g
As the intermolecular attractive forces between molecules increase in magnitude, do you expect each of the following to increase or decrease in magnitude? (g) critical temperature.
Problem 74b
The table below lists the density of O2 at various temperatures and at 1 atm. The normal melting point of O2 is 54 K.
(b) Over what temperature range is O2 a liquid?
- Suppose you have two colorless molecular liquids, one boiling at -84 °C, the other at 34 °C, both at atmospheric pressure. Which of the following statements is correct? For each statement that is not correct, modify the statement so that it is correct. (a) The higher-boiling liquid has greater total intermolecular forces than the lower-boiling liquid. (b) The lower-boiling liquid must consist of nonpolar molecules. (c) The lower-boiling liquid has a lower molecular weight than the higher-boiling liquid.
Problem 75
Problem 75d
Suppose you have two colorless molecular liquids, one boiling at - 84 °C, the other at 34 °C, and both at atmospheric 6 pressure. Which of the following statements is correct? For each statement that is not correct, modify the statement so that it is correct. (d) The two liquids have identical vapor pressures at their normal boiling points.
Problem 75e
Suppose you have two colorless molecular liquids, one boiling at - 84 °C, the other at 34 °C, and both at atmospheric 6 pressure. Which of the following statements is correct? For each statement that is not correct, modify the statement so that it is correct. (e) At - 84 °C both liquids have vapor pressures of 760 mm Hg.
Problem 76a
Two isomers of the planar compound 1,2-dichloroethylene are shown here.
(a) Which of the two isomers will have the stronger dipole– dipole forces?
Problem 78a
The table below shows the normal boiling points of benzene and benzene derivatives.
(a) How many of these compounds exhibit dispersion interactions?
Problem 78e
The table below shows the normal boiling points of benzene and benzene derivatives. (e) Why is the boiling point of phenol the highest of all?
Problem 81
Use the normal boiling points propane (C3H8) -42.1 °C butane (C4H10) -0.5 °C pentane (C5H12) 36.1 °C hexane (C6H14) 68.7 °C heptane (C7H16) 98.4 °C to estimate the normal boiling point of octane (C8H18). Explain the trend in the boiling points.
- One of the attractive features of ionic liquids is their low vapor pressure, which in turn tends to make them nonflammable. Why do you think ionic liquids have lower vapor pressures than most room-temperature molecular liquids?
Problem 82
Problem 83b
(b) A flask of water is connected to a vacuum pump. A few moments after the pump is turned on, the water begins to boil. After a few minutes, the water begins to freeze. Explain why these processes occur.
Problem 84a
The following table gives the vapor pressure of hexafluorobenzene (C6F6) as a function of temperature: (a) By plotting these data in a suitable fashion, determine whether the Clausius–Clapeyron equation (Equation 11.1) is obeyed. If it is obeyed, use your plot to determine ∆Hvap for C6F6.
Problem 85
Suppose the vapor pressure of a substance is measured at two different temperatures. (a) By using the Clausius–Clapeyron equation (Equation 11.1) derive the following relationship between the vapor pressures, P1 and P2, and the absolute temperatures at which they were measured, T1 and T2: (b) Gasoline is a mixture of hydrocarbons, a component of which is octane (CH3CH2CH2CH2CH2CH2CH2CH3). Octane has a vapor pressure of 13.95 torr at 25 °C and a vapor pressure of 144.78 torr at 75 °C. Use these data and the equation in part (a) to calculate the heat of vaporization of octane. (c) By using the equation in part (a) and the data given in part (b), calculate the normal boiling point of octane. Compare your answer to the one you obtained from Exercise 11.81. (d) Calculate the vapor pressure of octane at - 30 °C.
- The following data present the temperatures at which certain vapor pressures are achieved for dichloromethane (CH2Cl2) and methyl iodide (CH3I): (c) The order of volatility of these two substances changes as the temperature is increased. What quantity must be different for the two substances for this phenom- enon to occur?
Problem 86
Problem 87
Naphthalene (C10H8) is the main ingredient in traditional mothballs. Its normal melting point is 81 °C, its normal boiling point is 218 °C, and its triple point is 80 °C at 1000 Pa. Using the data, construct a phase diagram for naphthalene, labeling all the regions of your diagram.
- A watch with a liquid crystal display (LCD) does not function properly when it is exposed to low temperatures during a trip to Antarctica. Explain why the LCD might not function well at low temperature.
Problem 88