Assigned Homework Problems – Answer Key
CHM 218 (Dr. Tremain)
Chapter 14 – Group 14 Elements
1. a) Li2C2(s) + 2 H2O(l) àà 2 LiOH(aq) + C2H2(g)
b) SiO2(s) + 2 C(s) àà Si(l) + 2 CO(g)
c) CuO(s) + CO(g) àà Cu(s) + CO2(g)
d) Ca(OH)2(aq) + CO2(g) àà CaCO3(s) + H2O(l)
CaCO3(s) + CO2(g) + H2O(l) àà Ca(HCO3)2(s)
e) CH4(g) + 4 S(l) àà CS2(g) + 2 H2S(g)
f) SiO2(s) + 2 Na2CO3(l) àà Na4SiO4(s) + 2 CO2(g)
g) PbO2(s) + 4 HCl(aq) àà PbCl4(aq) + 2 H2O(l)
PbCl4(aq) àà PbCl2(s) + Cl2(g)
3. a) Catenation is the ability of an element to form chains of its atoms.
b) Aerogel is a silicate in which there are numerous cavities in the structure resulting in very low
densities.
c) Ceramics are non-metallic inorganic compounds prepared by high temperature synthesis.
d) Silicone is composed of chains of alternating silicon and oxygen atoms to which organic
(carbon-containing) side groups are attached.
5. Diamond is a very hard, transparent, colorless solid that is a good conductor of heat, but a
nonconductor of electricity. It is insoluble in all solvents and it is chemically unreactive except
upon heating in dioxygen. Graphite is a soft, slippery, black solid that is a poor conductor of heat
but a good conductor of electricity. It is insoluble in all solvents and will react chemically only with
very reactive elements such as dioxygen and difluorine. C60 is black and a nonconductor of heat
and electricity. It is soluble in many non-polar and low-polarity solvents and it is quite reactive
chemically.
7. Diamond and graphite both have network covalent bonded structures. The solvation process
cannot provide the energy necessary to break non-polar covalent bonds. The fullerenes consist of
discrete molecules, such as C60. These individual non-polar units can become solvated by non-
polar or low-polarity solvent molecules and hence dissolve.
15. As the central carbon atom must form two σσ bonds to the sulfur atoms, we assume that sp hybrid
orbitals are formed. Like carbon dioxide, we consider that the 2p orbitals at right angles to the sp
hybrid orbitals overlap with 3p orbitals of the sulfur to provide a pair of ππ bonds.
19. The synthesis of HFC-134a requires a complex, expensive multistep procedure. Also, higher
pressures are necessary for its liquefaction, compared with the CFCs, making it necessary to
completely replace the old refrigeration units when changing to HFC-134a.
