Download In Class Notes Week 9

42. Estimate Ho for forming 2 mol ammonia from molecular
nitrogen and molecular hydrogen. Is this reaction exothermic
or endothermic? (N2 has a triple bond.)
43. Estimate Ho for the conversion of 1 mol carbon monoxide
to carbon dioxide by combination with molecular oxygen. Is
this reaction exothermic or endothermic? (CO has a triple
bond.)
44. Which of the four molecules HF, HCl, HBr, and m has the
strongest chemical bond? Using bond energies, estimate the
Ho for the reaction of molecular hydrogen with each of the
gaseous molecular halogens: fluorine, chlorine, bromine, and
iodine. Which is the most exothermic reaction?
48. The molecule below is urea, a compound used in plastics
and fertilizers.
O
NH2
H2N
urea
(a) Which bonds in the molecule are polar and which are
nonpolar?
(b) Which is the most polar bond in the molecule? Which atom
is the partial negative end of this bond?
52. Write correct Lewis structures and assign a formal
charge to each atom.
(a) SO3
(b) C2N2 (atoms bonded in the order NCCN)
(c) NO2-
53. Write correct Lewis structures and assign a formal
charge to each atom.
(a) OCS
(b) HNC (atoms bonded in that order)
(c) CH3-
54. Write correct Lewis structures and assign a formal
charge to each atom.
(a) CH3CHO
(b) N3(c) CH3CN
60. These have two or more resonance structures. Write all
the resonance structures for each.
(a) Nitric acid
O
N+
O-
HO
nitric acid
(b) Nitrate ion NO3-
61. These have two or more resonance structures. Write all
the resonance structures for each molecule or ion.
(a) SO3
(b) SCN-
Exceptions to the Octet Rule
67. Write the Lewis structure for each of these molecules or
ions.
(a) BrF5
(b) lF5
(c) IBr2-
68. Write the Lewis structure for each of these molecules or
ions.
(a) BrF3
(b) I3(c) XeF4
69. Which of these elements can form compounds with five or
six pairs of valence electrons surrounding their atoms?
(a) C
(b) P
(c) °
(d) F
(e) Cl
(f) B
(g) Se
(h) Sn
71. All carbon-to-carbon bond lengths are identical in benzene.
Does this argue for or against the presence of C=C bonds in
benzene? Explain.
72. Three dibromobenzenes are known. Write the Lewis
structure and name for each compound.
74. Write the structural formula for 1,2-diiodobenzene (also
known as ortho-diiodobenzene). Write the structural formulas
for the meta and para isomers as well.
Biological Periodic Table
90. Make a list of the top ten most abundant essential elements needed by the human body.
91. Which types of compounds contain the majority of the
oxygen found in the human body?
92. (a) How are metals found in the body, as atoms or as ions?
(b) What are two uses for metals in the human body?
93. Distinguish between macrominerals and microminerals.
94. Which minerals are essential at smaller concentrations but
toxic at higher concentrations?