Unformatted text preview: bout 50 kJ/mol. How much does the ﬂow rate change when the temperature
changes from 10 C to 25 C?
10. In order to form a polymer, many identical small molecules are linked together in a
chemical reaction. The polymerization reaction is exothermic, or heat producing, and it
can be described as an Arrhenius process. The activation energy is typically on the order of 80 kJ/mol. How much does the reaction rate change if the temperature increases
11. Why are top-of-the-line electronic cable ends made using gold (contacts) rather than
steel, aluminum, or copper?
12. It is energetically an uphill battle to reduce Al2 O3 to 2Al and (1.5)O2 . Since the thermodynamics favor the oxide rather than the separate elements, how can a process exist
to reduce bauxite (the oxide of aluminum) to pure aluminum? SECTION 2.4
Primary Bonds 13. For each of the primary bond types answer the following questions:
a. Does this type of primary bond usually involve electronegative atoms, electropositive atoms, or both types of atoms?
b. Are the bonding electrons shared or transferred?
c. If the bonding electrons are shared, are they spatially localized or delocalized?
14. Determine the most likely type of primary bond in each of the following materials: O2 ,
NaF, InP, Ge, Mg, CaF2 , SiC, (CH2 )n, MgO, CaO.
15. Show how the four unpaired electrons in C form covalent bonds, say, with four H
atoms. That is, show electron sharing and application of the “ﬁlled valence shell rule.”
16. How does the coulombic force change with distance between charges? What other wellknown force shows this behavior? At what charge separation is dF (coulombic)/dx a
maximum? A minimum?
17. Deﬁne what is meant by the terms ionization potential and electron afﬁnity.
18. Why do covalent bonds form only between electronegative elements?
19. If O forms a covalent bond with itself and Si forms a covalent bond with itself, then is
it reasonable to suggest that Si @ O is a covalent bond?
20. Is it possible that a ce...
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