SOLVED

61) Which of the following involves delocalized Ï€ bonds? A) acetylene (C2H2) B) benzene (C6H6) C) carbon tetrachloride (CCl4) D) dichlorodifluoromethane (CF2Cl2) E) ethylene (C2H4) 62) If the HCOO- ion is described using delocalized electrons, why can the oxygen atoms not have sp3 hybrids? A) There must be an unhybridized p orbital to form the pi bond system. B) The s orbital must be unhybridized to form the pi bond system. C) There is no hybridization in systems with delocalized electrons. D) Molecular orbital theory does not include hybridization. E) The four lobes repel each other too strongly. 63) How would replacing one of benzene’s C atoms and the H atom attached to it with an N atom (C5H5N) affect the delocalized electrons? A) The molecule would not be stable. B) The N can have delocalized electrons like C. C) Only the five C atoms would be included in the delocalized electrons. D) There would be no delocalized electrons but a double bond between the N and a C. E) There would be no delocalized electrons but a double bond between the N and the C on each side of the N. 64) Which of the following does NOT involve any delocalized Ï€ bonds? A) acetate ion B) carbonate ion C) nitric acid D) nitrous acid E) ozone 65) Which of the following statements is INCORRECT? A) Delocalized pi orbitals are formed when electrons are shared by unhybridized p orbitals in more than two atoms. B) The band theory is a form of molecular orbital theory. C) In band theory, there are two bands. D) The valence band is at higher energy than the conduction band. E) An energy band partially filled with electrons is a conduction band. 66) Which of the following statements about extrinsic semiconductors is INCORRECT? A) They are generally made from pure Si or Ge with small amounts of impurities. B) n-type are those in which the impurity is an element of Group 15. C) p-type are those in which the impurity is an element of Group 13. D) The crystal need not be very pure before the impurity is added to produce the semiconductor. E) Boron is a common impurity in n-type extrinsic semiconductors. 67) The “electron-sea” model for bonding in metals, although an oversimplification, offers a reasonable explanation of all of the following metallic properties EXCEPT: A) ductility B) electrical conductivity C) gaseous diatomic metal molecules D) thermal conductivity E) malleability 68) The inclusion of a small amount of phosphorus in a crystal of pure germanium yields what kind of semiconductor? A) an insulator B) an amorphous solid C) n-type, in which extra electrons carry the current D) p-type, in which a deficiency of electrons carries the current E) p-n-p type 69) The inclusion of a small amount of aluminum in a crystal of pure germanium yields what kind of semiconductor? A) an insulator B) an amorphous solid C) n-type, in which extra electrons carry the current D) p-type, in which a deficiency of electrons carries the current E) p-n-p type 70) All of the following are p-type semiconductors EXCEPT: A) As in Si. B) Al in Si. C) B in Ge. D) In in Se.