1982 D
(a) Draw the Lewis electron-dot structures for CO32-, CO2, and CO, including resonance
structures where appropriate.
(b) Which of the three species has the shortest C-O bond length? Explain the reason for
your answer.
1991 D
Experimental data provide the basis for interpreting differences in properties of
substances.
TABLE 1
Melting
Electrical
Compound Point (ºC)
Conductivity of
Molten State (ohm-1)
BeCl2
405
0.086
MgCl2
714
> 20
SiCl4
-70
0
MgF2
1261
> 20
TABLE 2
Substance Bond Length
(angstroms)
F2
Br2
N2
1.42
2.28
1.09
Account for the differences in properties given in Tables 1 and 2 above in terms of the
differences in structure and bonding in each of the following pairs.
(a) MgCl2 and SiCl4
(c) F2 and Br2
(b) MgCl2 and MgF2
(d) F2 and N2
Questions 8–10 refer to the following diatomic species.
(A) Li2
(B) B2
(C) N2
(D) O2
(E) F2
8.
Has the largest bond–dissociation energy
9.
Has a bond order of 2
10. Contains 1 sigma (s) and 2 pi (_) bonds
Questions 8-9
(A) A network solid with covalent bonding
(B) A molecular solid with zero dipole moment
(C) A molecular solid with hydrogen bonding
(D) An ionic solid
(E) A metallic solid
8.
9.
Solid ethyl alcohol, C2H5OH
Silicon dioxide, SiO2
Which of the following molecules has the shortest bond length?
(A) N2
(C) Cl2
(E) I2
(B) O2
(D) Br2
Ion
Ionic Radius (pm)
Zn2+
74
2+
Ca
100
Ba2+
135
Based on the data in the table above, which of the following correctly predicts the relative
strength of the attraction of Zn2+, Ca2+, and Ba2+ ions to water molecules in a solution
from strongest to weakest, and provides the correct reason?
A) Zn2+ > Ca2+ > Ba2+ because the smaller ions have a stronger coulombic attraction to
water
B) Zn2+ > Ca2+ > Ba2+ because the smaller ions are more electronegative
C) Ba2+ > Ca2+ > Zn2+ because the larger ions are more polarizable
D) Ba2+ > Ca2+ > Zn2+ because the larger ions are less electronegative
Boiling Point (C)
NaF
1695
MgO
3600
Na+
Mg2+
FClO2Ionic Radius 76
72
133
181
140
(pm)
54. Based on the data in the tables above, which of the following statements provides the
best prediction for the boiling point of NaCl?
A) NaCl will have a lower boiling point than NaF because the coulombic
attractions are weaker in NaCl than in NaF
B) NaCl will have a boiling point between that of NaF and MgO because the
covalent character of the bonds in NaCl is intermediate between that of MgO
and NaF
C) NaCl will have a higher boiling point than MgO because the ions are spaced
farther apart in NaCl
D) NaCl will have a higher boiling point than MgO because the energy required
to transfer electrons from the anion to the cation is larger in NaCl than in
MgO
Compound
Molecular Formula Molar Mass (g/mol) Boiling Point (C)
Nonane
C9H20
128
151
2,3,4C5H9F3
126
89
trifluoropentane
Nonane and 2,3,4,-trifluoropentane have almost identical molar masses, but nonane has a
significantly higher boiling point. Which of the following statements best helps explain
this observation?
A) The C—F bond is easier to break than the C—H bond
B) The C—F bond is more polar than the C—H bond
C) The carbon chains are longer in nonane than they are in 2,3,4-trifluoropentane
D) The carbon chains are farther apart in a sample of nonane than they are in 2,3,4,trifluoropentane