課程名稱︰普通化學乙下
課程性質︰系定必修
課程教師︰林金全
開課學院：
開課系所︰材料系
考試日期（年月日）︰2008年4月29日
考試時限（分鐘）：160分鐘
是否需發放獎勵金：是
（如未明確表示，則不予發放）
試題 :
1. Values of measured bond energies may vary greatly depending on the
molecule studies. Consider the following reactions: (8%)
NCl3(g) -> NCl2(g) + Cl(g) ΔH=375KJ/mol
ONCl(g) -> NO(g) + Cl(g) ΔH=158KJ/mol
Rationalize the difference in the values of ΔH for these reactions, even
though each reaction appears to only involve the breaking of one N-Cl bond.
2. (1)If the force constant of NO is 1550 Nm^-2, determine the wave number of
a line in the infrared spectrum of NO. The atomic mass of N is 14.003
amu, and the atomic mass fo O is 15.995 amu. (5%)
(2)The microwave spectrum of CO shows that the transition from J=0 to J=1
requires electromagnetic radiation with a wavelength of 2.60 x 10^-3 m.
a. Calculate the bond length of CO. See (1) for the atomic mass of O.(5%)
b. Calculate the frequency of radiation absorbed in a rotational
transition from the second to the third excited states of CO. (5%)
3. (1) Draw the MO energy-level diagram for each of the following species.(8%)
(2) In terms of the molecular orbital model, which species in each of the
following two pairs will most likely be the one to gain an electron?
Explain.(8%)
CN or NO O2^2+ of N2^2+
4. A promising new material with great potential as fuel in solid rocket motors
is ammonium dinitramide, NH4N(NO2)2. (12%)
a. Draw Lewis structures (including resonance forms) for the dinitramide ion
N(NO2)2^-.
b. Ammonium dinitramide can decompose explosively to nitrogen, water, and
oxygen. Write a balance equation for this reaction and use bond energies
to estimate ΔH for the explosive decomposition of this compound.
d. To estimate ΔH from bond energies, you made several assumptions. What
are some of your assumptions ?
5. Predict the molecular structure and the bond angles for each of the
following. (12%)
a. XeCl2 b. ICl3 C. TeF4 d. PCl5
6. Acetic acid is responsible for the sour taste of vinegar. It can be
manufactures using the following reaction:
OH
|
CH3OH(g) + C≡H(g) -> CH3C＝O(l)
Use tabulated values of bond energies to estimate ΔH for this reaction.
Compare this result to the ΔH value calculated using standard enthalpies
of formation. Explain any discrepancies.(12%)
7. The treatment of a particle in a one-dimensional box can be extended to a
rectangular box of dimensions Lx, Ly, and Lz, yielding the following
expression for energy:
h^2 nx^2 ny^2 nz^2
E = -----(------ + ------ + ------)
8m Lx^2 Ly^2 Lz^2
The three quantum numbers nx, ny, and nz independently can assume only
integer values.
a. Determine the energies of the three lowest levels, assuming that the box
is cubic.(5%)
b. Describe the degeneracies of all the levels that correspond to quantum
numbers having values of 1 or 2. How will these degeneracies change in a
box where Lx≠Ly≠Lz? (5%)
8. (1) The wave function for 2Pz orbital in the hydrogen atom is
1 Z
Ψ2Pz = --------(---)^3/2σe^-σ/2 cosθ
4√(2π) a0
where a0 is the value for the radius of the first Bohr orbit in
meters (5.29x10^-11), σ is Z(r/a0), r is the value for the distance
from the nucleus in meters, and θ is an angle. Calculate the value of
Ψ2Pz at r=a0 for θ=0 (z axis) and for θ=90º (xy plane).(8%)
(2) For hydrogen atoms, the wave function for the state n=3, l=0, ml=0 is
1 1
Ψ300 = ---------(---)^3/2 (27-18σ+2σ^2)e^-σ/3
91√(3π) a0
where σ=r/a0 and a0 is the Bohr radius (5.29x10^-11). Calculate the
position of the nodes for this wave function.(8%)
Information:
(1)Bond energies
C≡O = 1072KJ/mol
C＝O = 745 KJ/mol
C－O = 358 KJ/mol
C－C = 347 KJ/mol
N－H = 391 KJ/mol
N－N = 160 KJ/mol
N＝N = 418 KJ/mol
N≡N = 947 KJ/mol
H－O = 467 KJ/mol
O＝O = 495 KJ/mol
N－O = 201 KJ/mol
N＝O = 607 KJ/mol
C－H = 413 KJ/mol
∴
(2)Standard enthalpies of formation
CH3OH(g) = -201 KJ/mol
CO(g) = -110.5 KJ/mol
Ch3COOH(l) -484 KJ/mol
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※ 編輯: NBL123 來自: 140.112.240.174 (04/29 18:59)