Back
Problem 119a
(a) The density of diamond is 3.5 g/cm3, and that of graphite is 2.3 g/cm3. Based on the structure of buckminsterfullerene, what would you expect its density to be relative to these other forms of carbon?
Problem 119b
(b) X-ray diffraction studies of buckminsterfullerene show that it has a face-centered cubic lattice of C60 molecules. The length of an edge of the unit cell is 14.2 Å. Calculate the density of buckminsterfullerene.
- When you shine light of band gap energy or higher on a semiconductor and promote electrons from the valence band to the conduction band, do you expect the conductivity of the semiconductor to (a) remain unchanged, (b) increase, or (c) decrease?
Problem 120
- Spinel is a mineral that contains 37.9% Al, 17.1% Mg, and 45.0% O, by mass, and has a density of 3.57 g/cm³. The unit cell is cubic with an edge length of 8.09 Å. How many atoms of each type are in the unit cell?
Problem 121
Problem 122a
(a) What are the C—C—C bond angles in diamond?
Problem 122c
(c) What atomic orbitals are involved in the stacking of graphite sheets with each other?
Problem 123
Employing the bond enthalpy values listed in Table 8.4, estimate the molar enthalpy change occurring upon (a) polymerization of ethylene. (b) formation of nylon 6,6. (c) formation of polyethylene terephthalate (PET).
Problem 123c
Employing the bond enthalpy values listed in Table 8.3 estimate the molar enthalpy change occurring upon c. formation of polyethylene terephthalate (PET).
Problem 124a
Although polyethylene can twist and turn in random ways, the most stable form is a linear one with the carbon backbone oriented as shown in the following figure:
The solid wedges in the figure indicate bonds from carbon that come out of the plane of the page; the dashed wedges indicate bonds that lie behind the plane of the page. (a) What is the hybridization of orbitals at each carbon atom? What angles do you expect between the bonds?
Problem 125a
(a) In polyvinyl chloride shown in Table 12.6, which bonds have the lowest average bond enthalpy?
Problem 127b
One method to synthesize ionic solids is by the heating of two reactants at high temperatures. Consider the reaction of FeO with TiO2 to form FeTiO3. Determine the amount of each of the two reactants to prepare 2.500 g FeTiO3, assuming the reaction goes to completion. (b) Calculate the formula weight of FeTiO3.
Problem 127d
One method to synthesize ionic solids is by the heating of two reactants at high temperatures. Consider the reaction of FeO with TiO2 to form FeTiO3. Determine the amount of each of the two reactants to prepare 2.500 g FeTiO3, assuming the reaction goes to completion. (d) Determine moles and mass (g) of FeO required.