推 jasonfghx :乙茶哥 12/02 22:12
推 xox1015 :乙茶神手 12/05 21:27
課程名稱︰普通化學一
課程性質︰必修
課程教師︰鄭原忠
開課學院：理學院
開課系所︰化學系
考試日期（年月日）︰100年11月30日
考試時限（分鐘）：120分鐘
是否需發放獎勵金：是
（如未明確表示，則不予發放）
試題 :
General Chemistry (I)
Mid-term Exam #2 Date: 11/30/2011
(110 points)
1.(5%) Write the chemical formulas for the following compounds:
(a) Silver cyanide
(b) Calcium hypochlorite
(c) Lithium hydride
(d) Sodium peroxide
(e) Ammonium dichromate
2.(10%) For each of the following molecules, give the Lewis structure and
or nonpolar) for each molecule.
(a) CBr4
(b) ClO2(-)
(c) ICl3
(d) PF3
(e) SO3
3.(25%)
(a)(5%) The Born-Oppenheimer approximation is the foundation of quantum
chemistry. State the approximation and explain how it is applied
in the MO theory of the hydrogen molecule.
(b)(5%) Explain what "LCAO-MO" is. Specify the two basis fundations used in
this model (denote the nature of the functions; there is no need to
give the exact mathematical formulas) and give the expression for
the two molecular orbitals. You should give symmetry arguments to
justify your results and label the two molecular orbitals based on
their symmetries.
(c)(5%) Give the normalization constant for each of the two molecular orbi-
tals in terms of the overlap integral of the two basis functions.
Draw a qualitative MO correlation diagram to denote the energy le-
vels of atomic and molecular orbitals
(d)(5%) Fill the MOs with two electrons and give the approximate electronic
wave function of the H2 molecule. Note that you need to consider
electron spin and indistinguishability of electrons.
(e)(5%) Use the MO correlation diagram to predict the bond orders of H2(+),
H2, He2(+), and He2. Sort the four molecules from low to high bond
energies.
4.(10%) Consider nitric oxide (NO), which is a major pollutant produced during
combustion.
(a)(5%) Draw a MO correlation diagram for the molecule, and denote its
electron configuration in the electronic groud state. What is the
bond order of NO?
(b)(5%) Predict whether the nitrosyl (NO(+)) will have a shorter or longer
bond than the NO molecule. Will NO(+) be paramagnetic like NO or
diamagnetic?
5.(10%) Compare the bonding in formic acid (HCOOH) with that in its conjugate
base formate ion (HCOO(-)). Draw Lewis diagrams, determine the hybri-
dization of the carbon atom, and give the molecular geometries. How do
the π orbitals differ in the two molecules? Give the bond orders to
the four C-O bonds in the two molecules and sort the four C-O bonds
from short to long bond lengths.
6.(10%) The molecular structure of cortisone is given on the right. (請自行用
wiki找"cortisone"英文版頁面, 出現的結構圖同考卷上的附圖) This steroid
is a drug that reduces inflammation and moderates allergic responses.
Name all the functional groups in the molecule. How many chiral centers
exist in the molecule? How many stereoisomers can be derived from this
molecule (ignore conformers)?
7.(10%) Use Hückel MO theory to construct π molecular orbitals for cyclobuta-
diene and predict molecular properties.
(a)(5%) Draw the MO correlation diagram and sketch the π MOs. Indicate the
degeneracies of these orbitals. The lowest energy MO is located at
the energy α+2β. Use this information to correctly assign the
energy lecels of all other MOs.
(b)(2%) Show the number of electrons occupying each π MO in the ground
state. Is cyclobutadiene paramagnetic in its ground state?
(c)(3%) Calculate the delocalization energy of cyclobutadiene. Is cyclobu-
tadiene aromatic?
8.(15%) The octahedral complex ion [MnCl6]^(3-) has more unpaired spins than
the octahedral complex ion [Mn(CN)6]^(3-).
(a)(5%) Give the splitting of the Mn d orbitals in the octahedral field.
Explain your results.
(b)(2%) How many unpaired electrons are present in the two complex ions?
(c)(3%) In each case, calculate the crystal field stabilization energy in
terms of Δo.
(d)(5%) Why Cl(-) is a weak-field ligand whereas CN(-) is a strong-field
ligand?
9.(15%) Answer ture or false for the following statements (3 points each):
(a) Order of absorption wavelengths: [Cr(CN)6]^(3-) > [Cr(NH3)6]^(3+) >
[Cr(H2O)6]^(3+).
(b) Order of the absolute values of hydration enthalpies: Mn(3+) > Cr(2+)
> Mn(2+) > Ca(2+).
(c) Butyl acetate can be produced from butanol and acetic acid.
(d) The bridge between photoelectron spectrum and MO theory is the
Koopman's theorem, which states that the orbital energy in the LCAO-MO
method is the ionization energy of an electron in the orbital.
(e) The LCAO-MO method always predicts a higher ground state energy than
the exact result.
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