A cube of solid benzene (C6H6; M = 78.11 g/mol) at its melting point and weighing 8.90 g is placed in 21.6 g of water at 39.0 °C. Given that the heat of fusion of benzene is 9.92 kJ/mol, to what temperature will the water have cooled by the time all of the benzene has melted. You can assume that the benzene remains at its melting point.

Diethyl ether (CH3CH2OCH2CH3) was one of the first chemicals used as an anesthetic. At 34.6C, diethyl ether has a vapor pressure of 760. torr, and at 17.9C, it has a vapor pressure of 400. torr. What is the H of vaporization for diethyl ether?

A 1.50-g sample of methanol (CH3OH) is placed in an evacuated 1.00-L container at 30 C. (a) Calculate the pressure in the container if all of the methanol is vaporized. (Assume the ideal gas law, PV = nRT.) (b) The vapor pressure of methanol at 30 C is 158 torr. What mass of methanol actually evaporates? Is liquid in equilibrium with vapor in the vessel?

Which would you expect to have the higher fusion enthalpy, N2 or I2? Explain your choice.

Chloroform, CHCl3, has a normal boiling point of 61C. Its vapor pressure at 43C is 0.526 atm. What is the concentration (in g/L) of CHCl3 when it saturates the air at 27C?

What are intermolecular forces? How do they differ from intramolecular forces? What are dipole-dipole forces? How do typical dipole-dipole forces differ from hydrogen bonding interactions? In what ways are they similar? What are London dispersion forces? How do typical London dispersion forces differ from dipole-dipole forces? In what ways are they similar? Describe the relationship between molecular size and strength of London dispersion forces. Place the major types of intermolecular forces in order of increasing strength. Is there some overlap? That is, can the strongest London dispersion forces be greater than some dipole-dipole forces? Give an example of such an instance.

Consider a substance X with a Hvap = 20.3 kJ/mol and Hfus = 9.0 kJ/mol. The melting point, freezing point, and heat capacities of both the solid and liquid X are identical to those of water. a If you place one beaker containing 50 g of X at 10C and another beaker with 50 g of H2O at 10C on a hot plate and start heating them, which material will reach the boiling point first? b Which of the materials from part a, X or H2O, would completely boil away first? c On a piece of graph paper, draw the heating curve for H2O and X. How do the heating curves reflect your answers from parts a and b?

p-Dichlorobenzene, C6H4Cl2, can be one of the ingredients in mothballs. Its vapor pressure at 20C is 0.40 mm Hg. (a) How many milligrams of C6H4Cl2 will sublime into an evacuated 750-mL flask at 20C? (b) If 5.0 mg of p-dichlorobenzene were put into an evacuated 750-mL flask, how many milligrams would remain in the solid phase? (c) What is the final pressure in an evacuated 500-mL flask at 20C that contains 2.00 mg of p-dichlorobenzene? Will there be any solid in the flask?

Intermolecular Forces The following picture represents atoms of hypothetical, nonmetallic, monatomic elements A, B, and C in a container at a temperature of 4 K (the piston maintains the pressure at 1 atm). None of these elements reacts with the others. a What is the state (solid, liquid, or gas) of each of the elements represented in the container? b Rank the elements in the container from greatest to least, in terms of intermolecular interactions. Explain your answer. c What type(s) of intermolecular attractions are present in each of these elements? d Explain which element has the greatest atomic mass. e One of the elements in the container has a normal boiling point of 2 K. Which element would that be (A, B, or C)? How do you know? f One of the elements has a melting point of 50 K. Which element would that be (A, B, or C)? Why? g The remaining element (the one you have yet to choose) has a normal boiling point of 25 K. Identify the element. Could this element have a freezing point of 7 K? Explain. h If you started heating the sample to 20 K, explain what you would observe with regard to the container and its contents during the heating. i Describe the container and its contents at 20 K. Describe (include a drawing) how the container and its contents look at 20 K. j Now you increase the temperature of the container to 30 K. Describe (include a drawing) how the container and its contents look at 30 K. Be sure to note any changes in going from 20 K to 30 K. k Finally, you heat the container to 60 K. Describe (include a drawing) how the container and its contents look at this temperature. Be sure to note any changes in going from 30K to 60k

Why does sweating cool the human body?